The biggest challenge when developing filtering face pieces (FFP) is to guarantee the required level of protection while keeping breathing resistance as low as possible. For instance, the FFP2 classification according to the DIN EN 149 standard requires that at an air flow rate of 95 l/min, particle penetration must not exceed 6% and breathing resistance must not exceed 2.4 mbar [1].

The aim of the SULA (“Safer and Easier Breathing”) research project was to significantly reduce both permeability and breathing resistance compared to the FFP2 classification by improving the production and processing of the nonwoven fabric and selecting the optimal (combination of) nonwoven media for the manufacture of the filter mask. Expertise from industry and application-oriented research was pooled to investigate the interaction of the individual process steps and their effects on the final product. The company Reifenhäuser Reicofil was responsible for producing nonwoven fabric samples and conducting experimental investigations into process design for the meltblown and hydrocharging processes.

IMSTec carried out material characterization of the samples and measured their filter performance, produced masks from the nonwoven fabrics, and tested them for compliance with the specifications. The main tasks for Fraunhofer ITWM were to create models and perform simulations for the most important steps in nonwoven fabric production, as well as to optimize the mask material. in such a way that the protection level is higher than required by the FFP2 standard and

For a meltblown nonwoven to meet the specifications, the fibers are electrostatically charged. In this project, the focus was on the hydrocharging technology, which is applied already during fiber production and thus promises an even distribution of the electric charge in the nonwoven. Extensive test runs on the nonwoven fabric line in conjunction with systematic simulation studies led to a significant improvement in the filter efficiency of the nonwoven fabrics without significantly increasing breathing resistance, as subsequent analysis of the filter performance showed.

The data on flow resistance and separation efficiency served as the basis for identifying models to predict filter performance. Linking these models to the manufacturing process made it possible to produce better nonwovens for personal protection. The models could also be used to find optimal combinations of the new nonwoven fabrics so that the final mask would have the desired improved properties.

In this presentation, we will introduce the project and the key aspects of the research and development work carried out and discuss the results. We will also address the insights gained and provide an outlook for the future.

Filtering facepiece (FFP) respirators (FFRs) are widely used to protect against airborne particles. While conventional FFPs provide no protection against gaseous pollutants, some commercial FFP-type masks now also incorporate small amounts of activated carbon and claim to reduce e.g. odours, nuisance gases or low-level organic vapours. However, such gas protection is rarely documented, and there is currently no standardized test method or certification standard for gas protection in FFP-type respirators.

In this study, the gas protection was evaluated against >100 ppm of cyclohexane for a range of commercially available FFP2- and FFP3-classed masks containing activated carbon from brands including 3M, Honeywell, Dräger, Moldex, and Uvex. Gas adsorption performance varied widely between the models, but was generally limited in terms of both initial protection factor and adsorption capacity. In some cases, activated carbon particles appeared to be fully embedded in binder material, rendering them ineffective. Increased flow rates and elevated humidity further reduced gas adsorption performance. Moisture uptake from exhaled air is particularly detrimental for activated carbon in these devices. This type of condensation can be particularly challenging in cold environments and in masks without exhalation valve. [1]

Overall, the results demonstrate that [...]

Conditions of asthma aggravates in patient due to severity of air pollution. Masks serve as a critical barrier, protecting individuals from exposure to polluted air. Research reports suggest majority of the inhaled air that people breathe-in passes through nose.

This design project proposes a 3D-structured, aesthetically appealing nose mask with replaceable filter media that not only offers efficient cleaning of inhaled polluted air but also ergonomic fit to the wearer. This mask is designed using advanced facial 3D scanning techniques, aligning it with United Nations Sustainable Development Goals (SDGs). The present work addresses the challenges associated with conventional masks, such as fit, comfort, filtration efficiency, and environmental sustainability. The proposed solution aims to enhance utility for users while minimizing ecological impact.

This research explores the complexities of mask design, including material selection, ergonomic considerations, and the integration of advanced filtration technologies to ensure comprehensive respiratory protection. The scope of this study encompasses the design, development, and an evaluation of a personalized 3D-printed nose mask, highlighting its effectiveness, sustainability, and practical applications in real-world scenarios.

Pulse-jet baghouses are used in the industry to remove particles from gases coming from industrial processes and being released to the atmosphere. The first objective of the pulse-jet baghouse is to limit the particle emission to the atmosphere according to the local regulations. The second objective is to control the energy consumption being principally due to the filters pressure drop and the compressed air use.

The objective of our study is to better understand the flow field of a pulse-jet baghouse commonly used in the industry and to improve it to increase its performances. The pulse-jet baghouse uses 54 bag filters (6 x 9, polyester medium, 54 m²) and is designed to work between 3200 and 7000 m³/h. Air enters at the top in the dusty part of the baghouse (there is a baffle to protect the filters facing the flow) and leaves after being filtered also at the top on the other side.

Measurements were carried out for 3 different air inlet locations (at the top, at the bottom and in the hopper), for 3 different air outlet locations at the top (on the other side, on the same side and at 90°), and for different air flow rate (3200, 5100 and 7000 m³/h). Measurements were conducted to characterize the flow field (air velocity cartography) inside the pulse-jet baghouse. The results show that the flow field is not [...] the opposite side of the air inlet. Calcium carbonate dust (9 µm (D₅₀), 1 g/m³) was used; this dust is representative of industrial applications and commonly used for baghouse testing. The final pressure drop for filters cleaning was set at 800 Pa. Some configurations are better than others based on residual pressure drop (obtained after filters cleaning), cycle length, particle emission, compressed air use and energy consumption.

A performance index was developed based on weighted parameters, particle emission, compressed air consumption and fan energy use. This index enables the ranking of different configurations and the identification of the optimal one. The use of the performance index can be applied to every pulse-jet baghouse used in the industry to improve its performances.

Bag filters are essential in industrial air pollution control, offering effective dust collection across diverse industries. The ProJet Mega® bag filter by Intensiv Filter Himenviro represents a significant advancement in filtration technology, supporting flow rates ranging from 20,000 m³/h to over 2,000,000 m³/h. This paper delves into the pretreatment, post-treatment, and operational dynamics of the ProJet Mega®, focusing on its modular design, advanced cleaning systems like the Coanda Injector, and the utilization of ProTex filter media. Pretreatment ensures optimal air quality before filtration by addressing parameters such as humidity, temperature, and particle load. Post-treatment concentrates on the treatment of clean gases and disposal of collected dust, ensuring compliance with emission standards. Using Computational Fluid Dynamics (CFD), the system optimizes flow, reducing differential pressure and energy costs. The paper also discusses performance enhancements, such as extended filter bag life, reduced operational costs, and improved carbon footprint, offering insights into its suitability for applications like cement kilns and rotary mills.

Purefrax® Hot Gas Filters (HGFs), also known as Ceramic Candles, are used for high temperature dust filtration and emission control. Where traditional filter bags can only be used up to temperatures of approximately 260°C, HGFs are typically used for dust filtration in the 300-550°C range with the possibility of use up to 900°C. Commonly, HGFs are selected to replace Electrostatic Precipitators and Cyclones, particularly for their greater filtration efficiency and capacity of high temperature operation.

Key Drivers for High-Performance Hot Gas Filter Adoption:

• High‑temperature operation for heat‑recovery.
• Expanding high temperature applications (e.g. Gasification).
• Use of catalyst for removal of harmful gases.

However, there are certain applications where the brittle ceramic material properties of standard HGFs can be problematic. Particularly in earthquake-prone regions but also heavy industrial applications where there are additional stresses or movement.

For example, the use of HGFs in facilities such as glass manufacturing is a well-accepted technology, but when we include the risk of earthquakes and the consequential furnace shutdown, there can be reluctance to use this technology. In cases like these, filter bags are adopted as a compromise. They are made of flexible fabric substrate and resilient to tensile and shear stress, however they can only be used in lower temperatures.

Enabling safe and reliable use of HGFs in environments where ceramic filters have traditionally been a barrier has been one of Alkegen’s primary research and development projects. Today, we are able to share our innovations in this area, announcing the introduction of our new reinforced HGFs, designed to enhance resilience, reliability and performance of HGFs in extreme environments.

The Innovation

The majority of HGF breakages in applications occur at the flange section. This is where the HGF element is subject to the most force, as the flange supports the weight of the whole filter (approximately 10kg for a 3m piece). Alkegen’s new...

Electrostatic precipitators (ESPs) are an attractive solution for removing airborne particles due to their low pressure drop, low energy consumption, and high filtration efficiency. Their main drawback, however, is ozone production, which has constrained their use in applications where people may be exposed to ozone. The aim of this work was to study the feasibility of using a small ESP for personal protection and as a supply-air filter in residential ventilation systems.

A miniature electrostatic precipitator was designed and constructed to evaluate its performance. The two-stage device consisted of a unipolar needle corona charger and a conventional parallel-plate collector. The objective was to determine whether efficient operation could be achieved with minimal ozone production and low power consumption. Filtration efficiency was measured using diethylhexyl sebacate (DEHS) test aerosol and an optical particle analyzer at an airflow rate of 95 L/min, corresponding to the flow rate used for testing P2/P3-class respirator filters. A target filtration efficiency of >94%, in accordance with the requirements for P2-grade filters, was achieved at a charger voltage of 6 kV and a charging current of 5.5 µA. At these operating conditions, the ozone concentration was 40 µg/m³, which is below the WHO guideline value of 100 µg/m³. Higher voltages further improved removal efficiency but at the cost of increased ozone production and power consumption.

To further reduce ozone concentration, an invention developed and patented by VTT researchers was evaluated. The approach employs collector plates coated with an ozone-reactive material...

The assessment of infection risk in indoor environments remains challenging, particularly with respect to airborne pathogens present as bioaerosols. In response to growing concerns about airborne transmission, a wide range of air cleaning technologies, including indoor room air cleaners and automotive cabin air filtration systems, have been developed to reduce human exposure.

Current standardized testing approaches predominantly rely on single-pass filtration efficiency measurements using non-biological surrogate aerosols such as plasticizer aerosols (e.g. DEHS) or mineral dusts (e.g. ISO 12103-1 A2 fine dust). While these methods provide valuable information on particle removal performance, they do not fully reflect real-life indoor conditions, where air is typically recirculated multiple times and pathogens exhibit biological properties that differ from those of inert test aerosols. Consequently, the performance of air cleaning systems under realistic multi-pass conditions and with respect to bioaerosol removal or inactivation remains insufficiently characterized, limiting their relevance for infection risk assessment.

To further explore the bioaerosol removal efficiency of air cleaning systems a new method was developed as part of the research project “AeroMobil”. Now the filtration and deactivation of viral or bacterial air pollutants is quantified in real-life conditions with a multi-pass approach As continuous air cleaning relies on the recirculation of indoor air over an extended time frame, the newly established method allows for bioaerosols to be injected into a test room where it is filtered and deactivated by the test object in recirculation by whatever mechanism of testing interest such as filtration, UV-decontamination, plasma inactivation, or others. Air sampling heads connected to a vacuum pump collect the bioaerosol particles for further microbiological analysis.

One project goal was to design the test setup in such way that allows for testing in a great variety of room configurations as well as inside of vehicle cabins and not be limited to simplified laboratory setups.

The multi-pass data generated in our test rooms and previous single-pass filtration efficiencies was integrated into a mathematical model to further expand the capabilities of air hygiene testing. This combines both results of the filter elements themselves as well as of the entire purifying machines. Known single-pass data can be entered into the model and used to calculate the theoretical performance of the air purifier in combination with the filter efficiency. The model additionally enables the upscaling of multi-pass results obtained in a test room to larger dimensions such as classrooms, while accounting for changes in room volume, the number of air purifiers, and the number of occupants, thereby allowing the impact of these parameters on aerosol concentration and infection risk to be assessed.

Microfiber release from textiles during domestic laundering has become an important environmental concern due to its contribution to airborne and waterborne microplastic pollution. While washing processes have been widely studied, microfiber generation during tumble drying remains less understood, particularly in heat pump dryers.

The experimental investigation systematically examined the root process parameters influencing lint release in heat pump tumble dryers. Thermo-mechanical drum–fabric interactions were evaluated across varying drum and fan speeds and temperature conditions using a 4 kg, 100% cotton test load at 60% initial moisture content. The study identified the dominant root causes of lint generation and informed the development of a new control algorithm aimed at reducing microfiber release

Experimantal results show that temperature alone is not a dominant factor. Higher drying temperatures increased thermal stress but shortened cycle duration, leading to no statistically significant difference in total microfiber release. Fabric moisture level was determined to be the dominant and critical parameter in microfiber release.Once the fabric moisture content decreased below a critical threshold, the fibers exhibited increased brittleness, leading to a pronounced rise in microfiber generation. Drum speed reduction strategies that did not account for the moisture-dependent behavior of the fabric showed only limited effectiveness.

Based on the experimental findings, a two-stage drum control strategy was implemented, applying higher drum speed in the early drying phase and reduced drum speed in the later phase. This strategy resulted in...

High‑efficiency particulate air (HEPA) and ultra‑low penetration air (ULPA) filters are key components of modern cleanroom technology in microelectronics, pharmaceutical manufacturing, medical device production, and advanced HVAC systems. Ensuring their reliable performance over the full lifecycle requires harmonized laboratory classification, production quality control, and in‑situ qualification in operating cleanrooms.

This contribution presents a structured, standards‑based approach that links type testing and production control of HEPA/ULPA filters according to ISO 29463‑4 and ‑5 with on‑site performance verification in accordance with ISO 14644‑3. ISO 29463 provides a framework for the determination of fractional efficiency and the most penetrating particle size (MPPS), the execution of scan‑based local efficiency and leak tests, and the measurement of integral efficiency to assign filters to defined efficiency classes. Building on this framework, we discuss the implementation of both local and integral measurements for different filter classes and geometries, highlighting the transition from flat‑sheet medium characterization to full‑size filter element testing.

Experimentally, we employ modular test stands designed for HEPA/ULPA filter evaluation, including manual and automated scanning systems as well as robot‑assisted setups for complex three‑dimensional filter geometries. These systems enable reproducible aerosol generation, well‑defined flow conditions and high‑resolution spatial mapping of local leakage and efficiency, while generating standardized digital test reports suitable for integration into quality management systems. We outline the methodology for transferring these laboratory and production concepts to in‑situ testing in installed cleanroom systems, with a focus on the selection of challenge aerosols, sampling strategies, scan patterns, and acceptance criteria (filter leak test) that are compatible with ISO 14644‑3 and practical constraints in operational facilities.

The paper concludes by proposing a consistent qualification strategy that spans initial filter development, series production, and periodic on‑site requalification...

Gas turbines are often operated in extreme climatic conditions, ranging from salty sea spray on offshore platforms to dusty desert environments. The reliability of these thermal power machines depends largely on the efficiency of the upstream air intake filtration systems. These filters must protect the gas turbine from high relative humidity, rain, salt particles from sea spray, and dust, thereby preventing corrosion, erosion, and fouling of turbine components.

To classify gas turbine air intake filters, the ISO 29461 standard has been developed. Due to the wide range of performance requirements, the standard is divided into four parts.

TOPAS GmbH has developed a dedicated test system and suitable test routines that cover parts 1, 2, and 4 of ISO 29461. The GTS 114 test system enables comprehensive characterization of gas turbine filters under largely realistic operating conditions. The test system allows controlled injection of salt aerosols, dust, water droplets (sea spray), and water vapor. The test system is capable of precisely and reproducibly controlling temperature and relative humidity within defined ranges, provided that the ambient conditions remain within the specified operating limits. Relative humidity levels of over 95% rH as well as in the range of 30–40% rH can be achieved, in accordance with the requirements of ISO 29461.

The presentation will demonstrate the current state of the automated test procedures as well as the test system itself. The test system faces numerous challenges, as a wide range of operating and environmental conditions must be realistically and reproducibly simulated. To ensure consistently high test quality, user-independent, fully automated test sequences can be carried out, extending over periods of up to 120 hours.

In addition, important key components for filter performance testing such as flame photometer, particle counter, humidifier, water spray systems and aerosol generators (DEHS, NaCl, KCl and ISO A2 fine dust) will be presented. As well as the evaluation of the obtained measurement data such as differential pressure, particle separation efficiency, water separation efficiency, dust loading, salt and water deluge challenge. The creation of a summary report, which includes all determined and recorded parameters for a direct interpretation of the test results, is also a part of the presentation.

The GTS 114 offers filter manufacturers a technologically advanced platform for optimizing product development. By realistically simulating high humidity, salt loads and high flow rates of up to 11,000 m³/h, the system provides reliable data on filter lifetime and separation efficiency that significantly exceed the capabilities of conventional standard test systems such as the ALF114.

As large infection outbreaks continue to occur, there is a constant need for evaluation whether air filters and products that claim to reduce pathogens through filtration are actually effective. Until now, however, there was no designated method to test filters directly with actual human pathogenic microorganisms or highly allergenic particles without the previous workaround of surrogate model organisms.

Currently, the filtration efficiency of filter media and filter elements such as indoor cabin filters, is predominantly characterised on filter test rigs or test chambers using standardized, non-biological test dusts & -aerosols, such as ISO 12103-1 A2 fine dust, DEHS or salt particles. The drawbacks of testing with non-biological particles and aerosols, being that they focus on particle size but do not factor in actual inactivation of potential biohazards. Air filtration tests with bioaerosols have been investigated in recent years, however, due to necessary safety precautions, test methods with actual human pathogenic microorganisms in distinctive test rigs are not widely available.

Therefore, a new filter test rig was developed to test not only flat sheet filter media but also filter elements for microbial reduction efficacy directly with human pathogenic microorganisms up to biosafety level 2 (BSL 2) as well as potentially highly allergenic particles. In order to achieve this, it was necessary to down scale the dimensions of the test rig in such a way that it could be fitted under commercially available biosafety cabinets used typically in microbiology laboratories of biosafety level 2, while still generating reproducible results under realistic conditions regarding airflow rates and particle nature. The configuration of the test rig was designed with a modular approach in mind.

By incorporating quickly interchangeable components, the test rig can be used for a great variety of biohazards, from pathogenic bacteria and viruses to highly allergenic fine dusts and pollen. The final test rig was validated against the well-established bioaerosol filtration tests methods currently performed at OFI.

Results demonstrate that it is possible to perform reproducible and highly sensitive tests for determination of microbial and allergenic reduction efficiency of critical human pathogens for a wide range of filter media and filter elements with the novel test rig under representative test conditions. Furthermore, the highly modular configuration opens new pathways for future planned endeavours, such as efficacy testing of air stream UV disinfection devices against airborne human pathogens.

Background
Semiconductor manufacturing relies on ultra clean gas and liquid delivery systems in which filtration performance directly influences process stability, equipment reliability, and output yield. As device geometries continue to shrink and process tolerances tighten, filtration media must maintain stable pore structures while minimizing particle release during continuous operation, pressure transients, and thermal cycling. Conventional filter media can exhibit particle shedding or pore instability, motivating the development of improved filtration solutions.

Aim
This work aims to investigate metal nanofiber-based filtration media engineered to provide precise and repeatable filtration performance while minimizing contamination risks in semiconductor manufacturing environments. The study focuses on filtration efficiency, particle retention, and structural stability under representative gas filtration conditions. Liquid filtration is out of the scope of this study.

Method
Nanofiber filtration media were fabricated using bundle drawing, webbing, and sintering processes. Different AISI 316L samples with fiber diameters ranging from 0.5 to 12 µm were manufactured. The samples also featured different basis weights (150–2400 g/m²) and porosities (50–90%). These were evaluated using a gas filtration setup.

Filtration performance was assessed through upstream and downstream particle counting using a polydisperse KCl aerosol.

Below the set up description:

• Instrument: SMPS (DMA + CPC) to obtain efficiency versus particle size and determine MPPS.
• Primary SMPS window: 5–500 nm (or down to 3 nm if the SMPS/CPC configuration supports stable measurement).
• Upper extension (optional): 800 nm–1 µm when feasible to ensure capture of an MPPS that may lie above the primary size range.

Results will be compared with those obtained using standard-sized fiber media.

Main Results

The paper will present quantified particle‑filtration efficiencies for filter media composed of fibers with different diameters. The results are expected to highlight the advantages of a specific nanometric fiber‑diameter range compared with coarser fibers, particularly in maintaining high particle‑capture efficiency and minimizing particle shedding under operating conditions representative of semiconductor‑manufacturing environments.

Air Permeability (AP) and Bubble Point Pressure (BPP) tests were conducted on flat‑sheet media samples at selected gas flow rates. AP measurements were performed at a differential pressure of ....

Filtration systems play a critical role in ensuring gas quality, protecting sensitive equipment, maintaining process stability, and optimising energy efficiency across the natural gas value chain. From upstream production and gas processing to transmission pipelines, compressor stations, pressure reduction stations, and distribution networks, gas streams are exposed to a wide range of contaminants, including solid particles, black powder, entrained liquids, corrosive compounds, oil aerosols, and moisture. Inadequate filtration leads to increased pressure drop (ΔP), reduced separation efficiency, higher compressor power consumption, accelerated corrosion, equipment fouling, and unplanned shutdowns.

Despite the strategic importance of filtration, current practices in many large-scale gas networks—particularly in developing and resource-constrained environments—remain fragmented. Filters are often selected, procured, installed, and maintained without a unified engineering framework. The absence of standardised selection criteria, performance verification tests, lifecycle management, and centralised data systems results in inconsistent filtration performance, unpredictable operational behaviour, and increased operational expenditures (OPEX). These shortcomings directly contribute to energy imbalance, reduced network reliability, and increased environmental and safety risks.

The growing demand for high-efficiency air filtration materials has intensified interest in multifunctional nanofiber media that combine particle capture, antimicrobial activity, and low airflow resistance. In this study, electrospun polyacrylonitrile (PAN) nanofibrous layers functionalized with a plant-derived antibacterial agent (thyme extract) were benchmarked against nanofibers containing a widely used synthetic additive (ZIF-8 metal–organic framework) to evaluate their suitability for advanced filtration applications.

Nanofiber membranes were produced under controlled electrospinning conditions with varying additive loadings and assessed in terms of structural characteristics, airflow resistance, particle filtration efficiency, and antibacterial performance. The results demonstrated that optimized nanofiber formulations achieved high submicron particle removal while maintaining low pressure drop, outperforming conventional melt-blown filtration media. Notably, nanofibers incorporating the natural antibacterial agent exhibited enhanced bacterial inactivation over typical mask usage periods, without compromising filtration performance or breathability.

Beyond filtration efficiency, the findings highlight the potential advantages of bio-based functional additives in reducing concerns related to toxicity, environmental release, and long-term exposure associated with synthetic antimicrobial agents. From an industrial perspective, these results support the feasibility of integrating natural antibacterial compounds into electrospun filtration layers as a sustainable alternative for next-generation face masks and air filtration systems. This work provides practical insight into the design of multifunctional nanofiber filter media and contributes to the development of safer, environmentally responsible filtration technologies aligned with emerging regulatory and sustainability requirements in the filtration industry.

In 2024, IEC 63086-2-1 was published as the first international testing standard for measuring the performance of air cleaners with particulate pollutants. For measuring particles in the size range from 0.1 – 1 µm, the standard requires the use of Optical Particle Size Spectrometers (OPSS), whereas the total number concentration including also ultrafine particles <0.1 µm is measured with Condensation Particles Counters (CPC). However, the standard deliberately refrains from prescribing specific models. Moreover, it allows either cigarette smoke or potassium chloride (KCl) as two interchangeable test aerosols and leaves for the latter the flexibility to neutralize the particles or not. So far, there has been no systematic study on the effect of these flexibilities in the choice of the measurement instrument, test aerosol and neutralization on the measurement results.

To address these questions, they were tackled in a detailed investigation using three different air cleaners. The filter types of the air cleaners were an H13 filter in accordance with EN 1822-1 (negligible particle size dependence), a commonly used electret filter (moderate particle size dependence), and a completely discharged electret filter (pronounced particle size dependence). The air cleaners were tested using the methods of IEC 63086-2-1 with ten different measurement instruments in parallel. Besides a CPC and five different OPSS models, also a Mobility Particle Size Spectrometer (MPSS), a Fast Mobility Particle Sizer (FMPS), and two appliances based on the principle of unipolar diffusion charging were used. The tests were performed with cigarette smoke as well as either neutralized or not neutralized KCl particles. From fitting the exponential decay curves with and without air cleaner, the size-dependent Clean Air Delivery Rate (CADR) was derived and compared between the different instruments, test aerosols, and neutralization stages.

For the integrated size range from 0.3 µm to 1 µm, all OPSS showed

In 2024, IEC 63086-2-1 was published as the first international testing standard for measuring the performance of air cleaners with particulate pollutants. For measuring particles in the size range from 0.1 – 1 µm, the standard requires the use of Optical Particle Size Spectrometers (OPSS), whereas the total number concentration including also ultrafine particles <0.1 µm is measured with Condensation Particles Counters (CPC). However, the standard deliberately refrains from prescribing specific models. Moreover, it allows either cigarette smoke or potassium chloride (KCl) as two interchangeable test aerosols and leaves for the latter the flexibility to neutralize the particles or not. So far, there has been no systematic study on the effect of these flexibilities in the choice of the measurement instrument, test aerosol and neutralization on the measurement results.

To address these questions, they were tackled in a detailed investigation using three different air cleaners. The filter types of the air cleaners were an H13 filter in accordance with EN 1822-1 (negligible particle size dependence), a commonly used electret filter (moderate particle size dependence), and a completely discharged electret filter (pronounced particle size dependence). The air cleaners were tested using the methods of IEC 63086-2-1 with ten different measurement instruments in parallel. Besides a CPC and five different OPSS models, also a Mobility Particle Size Spectrometer (MPSS), a Fast Mobility Particle Sizer (FMPS), and two appliances based on the principle of unipolar diffusion charging were used. The tests were performed with cigarette smoke as well as either neutralized or not neutralized KCl particles. From fitting the exponential decay curves with and without air cleaner, the size-dependent Clean Air Delivery Rate (CADR) was derived and compared between the different instruments, test aerosols, and neutralization stages.

For the integrated size range from 0.3 µm to 1 µm, all OPSS showed ...

Stand-alone air cleaners are most often characterized using initial Clean Air Delivery Rate (CADR). While this metric provides a convenient basis for comparison, it offers limited insight into how performance changes as particulate matter accumulates within the system. This study examines performance degradation in commercially available stand-alone air cleaners under progressive particle loading using controlled laboratory testing, with a focus on cumulative clean mass (CCM) and changes in effective CADR.

All testing was conducted in a controlled dust chamber to enable repeatable evaluation of degradation behavior while minimizing environmental variability. The tested devices represent two distinct particle removal approaches: several air purifiers based on high-efficiency fibrous filtration (HEPA-based systems) and one electrostatic air purifier employing a patented particle collection technology. Initial CADR measurements were performed following established procedures, after which each unit was subjected to incremental loading using ISO 12103-1 A2 fine test dust. CADR measurements were repeated after each loading step to track performance as a function of accumulated particulate mass.

Although the mechanically filtered air purifiers demonstrated comparable initial CADR values, their responses to dust loading differed substantially. In several cases, effective clean air delivery declined rapidly as loading increased, consistent with rising flow resistance through dense fibrous media. The electrostatic air purifier exhibited a more gradual reduction in delivered clean air under similar loading conditions, indicating lower sensitivity to pressure-drop-driven airflow loss. These results suggest that initial CADR alone is a poor predictor of sustained performance and that the underlying particle collection mechanism plays a central role in determining degradation behavior.

The findings highlight the value of loading-dependent performance evaluation and demonstrate how controlled dust chamber testing can be used to compare long-term performance trends across different air cleaning technologies in a repeatable and technically meaningful manner.

This study investigates the relationship between filter thickness and air purifiers' Clean Air Delivery Rate (CADR). Despite theoretical analysis of optimal CADR filter thickness, experimental validation has been lacking. This research addresses this gap by testing four filter brands and four fan powers to determine the optimal configuration for maximum CADR. A homemade air purifier with varying filter thicknesses and fan powers was utilized. Filtration efficiency was assessed by measuring particulate matter upstream and downstream of the air purifier using a Scanning Mobility Particle Sizer. CADR was calculated via the single-pass method.

Results indicate that filtration efficiency increases with thicker filters; however, the optimal CADR is achieved at a specific filter thickness. For instance, with a fan power of 2.7 W, optimal CADR corresponded to [...] filtration efficiency for 100 nm particles and [...] for Most Penetrating Particle Size (MPPS) particles (240–420 nm). When the same filter brand (Filter M) was used with varying fan powers (2.7–23.4 W), the highest CADR occurred consistently at around [...] filtration efficiency, irrespective of fan power, with MPPS ranging from 200 to 320 nm.

The study concludes that for each fan and filter combination, an optimal filter thickness exists to maximize CADR, which is crucial for enhancing air purifier efficiency and longevity. The findings recommend slightly reducing filter thickness below the optimal CADR thickness to prolong filter life while maintaining effectiveness. This study provides practical insights for improving the design and performance of air purifiers used in indoor environments.

Field testing experience of high efficiency flue gas filtration impact on amine carbon capture plant performance

More stringent emission limit values and the integration of carbon capture (CC) technologies into industrial plants introduces more stringent requirements on upstream flue gas cleaning performance in the fabric filter. Fine particulate matter, aerosols, acid gases, and trace contaminants can negatively impact CC system availability, solvent stability, carbon capture efficiency, and operational costs. Consequently, high performance upstream flue gas cleaning and filter bags with high separation efficiency is a fundamental prerequisite to future‑proof plants for carbon capture.

Fabric Filters (FF) combined with dry flue gas treatment systems, such as the ANDRITZ NID process, provide a robust and proven solution to achieve ultra‑low particulate emissions and stable flue gas conditions.

Andritz together with AWG have performed field testing of an amine-based carbon capture pilot at the AWG Wuppertal waste to energy plant.

AWG Wuppertal has been operating since 1976, burning ~415,000 t/a of waste to produce 130 000MWh electricity, and 470 000MWh of heat to the corridor Elberfeld → Barmen → Oberbarmen, Küllenhahn → Ronsdorf, and Elberfeld‑Süd.

A. Flue‑gas cleaning includes six boilers with electrostatic precipitators for primary de dusting, Fabric filter and ANDRITZ NID with integrated fabric filter, and advanced stages HOK (activated‑coke) and SCR (selective catalytic reduction). The performance of each of these systems determines the quality of gas delivered to any downstream CCS unit impacting performance, operating cost and maintenance.

Field experience from AWG Wuppertal, where a carbon capture pilot plant has been operated downstream of an ANDRITZ NID system. For cost efficient and reliable carbon capture performance the field test shows the importance of very high performing fabric filter upstream the carbon capture system.

The simultaneous removal of particulate matter (PM) and nitrogen oxides (NOx) in biomass and waste incineration facilities remains challenging due to space limitations, variable operating conditions, and the complexity of multi-unit emission control systems. In previous pilot-scale tests, pleated filter bags incorporating SCR pellet catalyst cartridges demonstrated the technical feasibility of integrated PM filtration and NOx reduction, showing stable filtration behavior and effective DeNOx performance under controlled conditions. Building on these pilot-scale results, the present study advances the technology to an industrial-scale field demonstration under real plant operation.

Following pilot validation, pleated SCR pellet catalyst filter bags were installed in a wood waste incineration boiler and operated as part of the plant’s routine emission control system. The demonstration aimed to verify long-term operational stability, scalability, and reliability under fluctuating flue gas temperature, dust loading, and boiler load conditions typical of industrial biomass incineration. Key performance indicators included PM removal efficiency, NOx conversion efficiency, pressure drop evolution, and ammonia injection behavior.

The industrial-scale operation confirmed that the pleated configuration ensured stable dust cake formation and controlled pressure drop during extended continuous operation. Simultaneously, the integrated SCR pellet catalyst cartridges maintained consistent NOx reduction performance without adversely affecting filtration characteristics or inducing abnormal pressure increase. No mechanical damage or catalyst-related operational issues were observed during the field demonstration period.

The results demonstrate a clear ...

ABSTRACT

Air pollution is a critical global public health and environmental challenge. With an estimated 8.1 million premature deaths annually, it ranks as the second leading cause of mortality worldwide. According to the World Health Organization, approximately 99% of the global population is exposed to air pollutant concentrations exceeding recommended guideline limits. Beyond its health impacts, air pollution also contributes significantly to environmental degradation and greenhouse gas emissions, largely driven by increasing urbanization and industrialization.

Conventional air treatment technologies rely predominantly on activated carbon, which accounts for nearly 90% of industrial air filtration applications for volatile organic compounds (VOCs) and odor removal. However, these systems suffer from several limitations, including limited performances, high energy consumption, substantial carbon footprint, rapid saturation leading to high maintenance requirement and tremendous waste generation. In the context of increasingly stringent European air quality regulations on industries, the development of advanced, efficient, and sustainable air purification technologies has become essential to sustain our industry while protecting the population health and the planet.

To address these challenges, Purenat has developed an innovative photocatalytic filtration medium inspired by diatoms, known for their exceptional photosynthetic efficiency. This biomimetic solution enables the transformation of airborne pollutants through oxidation and reduction reactions into harmless molecules like water vapor. Unlike conventional coated photocatalytic materials, the active agents are embedded directly within the fiber core of a textile structure, optimizing photocatalytic performance while preventing the release of secondary hazardous compounds. This approach offers a durable and cost-effective alternative to traditional air filtration technologies.

Over the past year, relevant pilot projects were conducted at industrial sites across France and Europe, covering diverse sectors including livestock farming, food processing, chemical manufacturing, and the fragrance industry. These trials were performed under real operating conditions to evaluate the efficiency, robustness, and industrial scalability of the photocatalytic filtration system. The main outcomes can be summarized as follows:

• High Performance

The system demonstrated strong depollution efficiency for complex mixtures of volatile organic compounds, involving dozens of distinct pollutants. High abatement efficiencies were observed for a wide range of carbon-, oxygen-, and hydrogen-based compounds, including odors, alcohols, aldehydes, ketones, aromatics, and mercaptans, under single-pass industrial operating conditions.

• Versatility and Integrability

The filtration units showed strong adaptability to existing industrial infrastructures and were designed to be directly connected to current air treatment installations, requiring minimal retrofit. Real-time monitoring of inlet and outlet VOC concentrations enabled on-site performance assessment and operational parameter adjustment during pilot operation.

• Energy Efficiency, Durability, and Maintenance

The technology exhibited a significantly reduced energy demand compared to actual conventional air treatment systems, characterized by low pressure drops. Photocatalytic activation relies on low-energy UV-A LED sources and requires only a standard 16 A electrical control unit, indicating limited electrical power demand. Owing to the non-saturating nature of the photocatalytic degradation mechanism, maintenance requirements were substantially reduced, with filter replacement required only after approximately 25,000 hours of operation, thereby limiting operational downtime and waste generation.

In response to increasing regulatory, environmental, and public health constraints, these results highlight the potential of photocatalytic textile-based filtration as a robust and scalable approach for industrial air treatment. By combining high depollution efficiency, operational flexibility, and reduced energy and maintenance constraints, this technology addresses key limitations of conventional air purification systems and opens new perspectives for sustainable industrial air quality management.

Air quality at metro platforms is influenced by train‑induced particle resuspension, abrasion processes, and complex airflow patterns. Within the Horizon Europe project AeroSolfd, we assessed how filtration solutions and optimized purifier placement can reduce PM exposure in semi‑enclosed underground stations. CFD simulations were applied to identify zones of high particle concentration and guide the placement of air purifiers, followed by a month‑long demonstration at a Lisbon metro station using both scientific‑grade instruments and distributed low‑cost sensors.

The AeroSolfd measurements confirmed two characteristic PM zones predicted by CFD: an HVAC‑supported cleaner zone and a high‑exposure zone where the ventilation system has limited effect. Scientific grade instruments were placed in one location, while low‑cost sensors enabled detailed spatial mapping. To compare similar use cases with and without air filtration, a detailed test plan was developed and optimized during the campaign. Duration of one operation mode could be one full day, half a day or two hours thereby also accounting for weekdays and weekends or holidays.

We will present results of the data analysis, show the challenges of measuring particle concentrations at metro stations, and discuss in detail the consequences of different approaches for data analysis to obtain solid values for evaluating filtration efficiency. The study shows that care must be taken in attempting to correct measurements from different devices. The results demonstrate the potential of well-placed air purifiers and hybrid operation with a stationary HVAC system to improve air quality at the platform.

Imagine a walk through a park on a hot summer day – the air not only feels cooler, but also fresher and cleaner than in the surrounding urban canyons. You may be wondering, “What potential do plants have for purifying the air and are they suitable for replacing professional filter media?” The ILK has investigated these questions in recent years, starting with shrubbery placed in a test channel. Its separation efficiency against the test dust Arizona fine was sobering. In further studies cushion moss showed promising separation results (see Fig 1). Based on these findings, the ILK Dresden is currently working on topics related to mosses as air filters.

Numerous further measurements were carried out under laboratory conditions and during field tests to understand the possibilities and limitations of this biological filter materials. An important focus is on the basic requirements of the moss – it should be vital and actively aerated.

Results of the investigations will be presented in more detail in the lecture.

Awareness of the importance of air quality for Human health and well-being has increased significantly over the past 15 years, leading to stricter performance requirements for air filtration systems. However, air quality challenges extend far beyond particulate removal: harmful gaseous pollutants such as VOCs, NOx, and SO₂ can easily pass through conventional filter media, impacting health, comfort, and overall performance.

At the same time, the emergence of new vehicle technologies replacing traditional combustion engines has created the need for advanced filtration solutions to protect sensitive and costly components—such as catalysts used in fuel cell vehicles—from gaseous contaminants.

To meet these growing needs, Ahlstrom, a global leader in sustainable and innovative fiber-based materials, has developed a new production platform for molecular filtration media designed to efficiently remove particles, fine particles, and harmful gases simultaneously pollutants. More specifically, target markets include cabin air, HVAC systems, and fuel cell air intake filtration supporting the shift toward Non-Combustion Engine vehicles.

From a technological perspective, gaseous pollutant removal relies on mechanisms fundamentally different from those used for particulate filtration, and most applications require the use of solid adsorbents. These adsorbents range from granular activated carbon to more advanced materials such as impregnated activated carbons or ion exchange resins, depending on the target contaminants, application environment, and specific requirements. In this context, the new Ahlstrom platform—PurXcel™—was designed to provide high versatility and flexibility, both in the choice and combination of solid adsorbents, and in the configuration of the particle filtration layer, which can range from standard electrostatically charged materials to multilayer solutions combining charged media with advanced electrospun nanofibers.

This article and presentation will detail two concrete examples demonstrating how this platform enables innovative solutions in premium cabin air filtration and fuel cell air intake applications. The first example highlights the benefits of electrospun nanofibers compared to conventional charged media, while the second showcases the potential of ion exchange resins for removing basic gas contaminants such as NH₃.

Nonwoven filters are widely used today to reduce emissions - for example, to improve indoor air quality or to protect technical equipment from dust exposure. Electret filters make it possible to increase the separation efficiency of a nonwoven filter without increasing the pressure drop. This allows the same cleaning performance to be achieved with lower energy consumption. In electret filters, the fibers are electrically charged so that electrostatic forces augment the purely mechanical separation mechanisms.

However, it is well known that the effect of this electrostatic charge diminishes with increasing operating time. The investigations presented here focus on liquid aerosol particles (droplets), since ageing caused by solid particles has previously been attributed mainly to charge neutralization [1]. In contrast, the influence of water droplets has already been examined experimentally and numerically [2,3]. If droplets remain within the filter medium, continued loading is expected to lead to coalescence, thereby altering both the electric field and the flow field within the filter structure. The interaction between droplets and the filter surface was investigated for various liquids using a contact angle measuring device (model OCA 15 EC, DataPhysics Instruments GmbH).

The liquids considered were water, ethanol, isopropanol, glycerin, DEHS, and paraffin oil. To additionally validate the results at the material level, measurements were performed on plastic plates made from five different raw materials that represent the common base materials of electret filters...

At Alkegen, we have studied the effect of ageing on the efficiency of fine fiber Meltblown in dynamic conditions. One HVAC grade MB7073 with an efficiency ePM1 75% according to ISO 16890 has been selected for this study. The meltblown media was produced in‑house by Alkegen using proprietary fine‑fiber technology.

This grade has filtered ambient air (rural environment) at media velocity 10.5 cm/s during the seven-month study.Temperature and relative humidity were recorded throughout the study.

Filtration properties – efficiency with KCl aerosol and pressure drop – were measured regularly during the ageing study, which was conducted at Alkegen’s filtration laboratories under controlled conditions. Over the seven-month study, efficiency remains steady and pressure drop increases slightly.

This stability can be explained by production on state-of-the-art equipment, and optimization of the additives used. These results demonstrate that the material maintains stable efficiency and acceptable pressure drop over seven months of real‑environment exposure, confirming its suitability for long‑term HVAC filtration applications...

Air-purification technology company Agentis Air will share the findings from a study on “Optimizing the Use of Room Air Purifiers in Combination with HVAC Filters for IAQ and Energy Efficiency”.

The paper explores the relationship between room air purifiers and HVAC filtration and how to optimize indoor air quality while minimizing energy use. The study determines this relationship at a variety of particulate levels, with fine and ultra-fine particles, a variety of HVAC operating conditions (such as air circulation rates and MERV ratings), and a variety of CADR levels for the subject room air purifiers.

The study has added relevance considering the new ASHRAE Standard 241: Control of Infectious Aerosols, which establishes an equivalent clean airflow (ECAi) formula that includes the use of room air purifiers, as a supplement to HVAC systems, to remove fine and ultrafine particle such as viruses and other pathogens. In the face of the serious and wide-ranging threat presented by airborne pathogens and poor indoor air quality, the HVAC-only solution—using higher MERV-rated filters—creates new problems, as these filters have backpressure that often exceeds the capacity of the HVAC systems in which they are installed. Even when compatible, high-backpressure filters also use more energy and require frequent filter changes, making them more expensive to maintain and environmentally unfriendly. As the study indicates, using appropriate room air purifiers in tandem with standard HVAC systems can reduce the energy penalty while achieving ultrafine particle filtration goals....

The processing of granular materials is often associated with dust emissions that arise from the mechanical or fluid-induced detachment of microscale dust particles adhering to macroscale bulk particles. The dustiness of granular materials depends, among other factors, on the adhesive forces between individual particles. Moisture content, which is governed by the ambient relative humidity, influences these interparticle adhesive forces and thus affects dust emission behavior. For the numerical prediction of dust emissions, a quantitative determination of interparticle forces is therefore essential. Consequently, investigating the influence of moisture content on adhesion forces between particles in bulk materials is crucial for understanding and predicting dust emissions. One method for measuring adhesive forces at the particle scale is atomic force microscopy (AFM).

This study presents an experimental setup designed to determine the adhesive forces between microscale and macroscale particles. The measurements are carried out in a custom-built climate chamber equipped with integrated humidification and dehumidification units, ensuring a defined relative humidity during the measurement process. Force-distance curves are recorded using an AFM and subsequently analyzed to quantify the adhesion forces. By systematically varying the relative humidity in each measurement series, its influence can be investigated in a controlled manner.

The study reports initial measurement results, identifies key challenges, and outlines corresponding solution approaches....

The control of particulate matter emissions in the steel industry is critical to ensuring compliance with environmental regulations and mitigating health risks. This study investigates the efficiency and durability of meta-aramid filter bags, comparing media produced by needle punching and hydroentanglement, in both virgin condition and after laboratory aging. The objective is to diagnose operational failures and analyze the energy consumption associated with the filtration process.

The methodology included the physicochemical characterization of particulate matter generated during the desulfurization process, as well as the structural analysis of the filter media (basis weight, thickness, air permeability, and fiber diameter). Samples were collected along the length of the filter bags in order to assess fiber heterogeneity. Filtration performance was evaluated through tests conducted in accordance with VDI 3926, covering the operating stages of new filter operation, artificial aging, stabilization, and aged filter operation, with continuous monitoring of pressure drop and collection efficiency. Preliminary scanning electron microscopy (SEM) results indicated that the desulfurization particulate matter consists of ...

A continuous filtration process that starts with a new, particle-free filter medium usually goes through the following phases in the typical theoretical description: The initial depth filtration in the given filter medium, the clogging phase in the given filter medium and the cake-forming filtration. These successive phases have been described using different modeling concepts, which make a holistic view of the entire filtration process difficult.

In the new multi-layer construction model presented by Zhang, the particle separation takes place during the entire filtration process in two coexisting filtering systems: In the case of a fiber layer as a filter medium, a fiber packing represents the one filtering system. All particles deposited in and on the fiber packing are regarded as the other coexisting filtering system, in which all these particles can be described together in form of a granular bed. Model calculation of the continuous filtration process can be carried out on this basis.

This multi-layer construction model does not consider interactions between the filtering elements or the filtering systems, such as momentum transfer and therefore no movement or release of already deposited particles, the reduction of the filtering surface of the existing filtering elements or other effects. The modeling of the reduction of the effective filtering surface due to particle contacts and its integration into the multi-layer construction model of Zhang is subject of this contribution. The decrease in the effective filtering surface of the fiber packing can be taken into account using information about the number of contact points between fiber and deposited particles, whereas the describing of the reduction of the effective filtering surface of the granular bed is more difficult. One approach is to apply the traditional dendrite model with a corresponding adjustment. The results of the improved model calculation, taking interactions into account, are compared with the results obtained without these interactions...

It is well known that both the separation efficiency and the corresponding pressure loss of a depth filter increase with the increasing dust load on the filter – apart from possible re-release of deposited dust particles, e.g., due to strongly varying gas volume flows. The corresponding time behavior of depth filters is referred to as filtration kinetics. Looking at the positive side of filtration kinetics, the filtration kinetics of a depth filter offer the possibility of subsequently adjusting the separation behavior of a given depth filter by means of targeted preloading of the filter. “Targeted preloading” here refers to the controlled loading of a depth filter with a defined quantity of defined particle fractions before the filter is actually used in order to achieve improved, individual separation behavior of the respective depth filter without structural/design changes.

This paper presents a model-based theoretical study using a recently developed multi-layer model with offset for cake growth, which enables the description of particle separation during the entire filtration process with a holistic, coherent model concept – i.e., without model switching between depth and surface filtration. The results from model calculations based on examples are intended to show whether targeted preloading can theoretically be a useful filter solution in specific application scenarios. To this end, not only the separation behavior and flow resistance at the beginning of the filtration process are presented, but also their time behavior during ongoing filter operation in order to achieve a holistic evaluation...

In the context of increasingly stringent occupational health and safety requirements, the testing of welding fume separation systems is of significant importance for the safeguarding of occupational health and environmental protection. Welding fumes contain a complex mixture of particulate and gaseous hazardous substances, including metals and metal oxides such as manganese, nickel, and chromium (VI). These substances pose a significant toxicological risk, the extent of which depends on the material and welding process. This is particularly pertinent in context of the recent reduction in occupational exposure limits for A-dust and specific metals.

The effectiveness of high-performance collection and separation systems can only be reliably assessed using standardised test methods. The welding fume test is performed on a dedicated test bench with an integrated chamber for the separator system. After system commissioning and setting the airflow according to manufacturer specifications, welding fumes are generated under controlled and reproducible conditions. The test consists of defined welding phases, during which raw and purified gas samples are taken to determine the filter separation rate.

The ILK Dresden has developed and validated a test method for these high requirements to meet the provisions of DIN EN ISO 21904-2, while also determining the separation effect of welding fume separators for manganese.

A key problem in welding fume testing arises from the low concentration range and the very low limit values for individual hazardous substances (especially for manganese), particularly in the case of welding high-alloy steels. The clean air concentrations derived from this are sometimes in the low end of the analytical detection range, meaning that both the measurement technology and sampling procedures must meet high standards The poster will provide a comprehensive overview of the reliable implementation and solutions of welding fume tests, as well as information about the danger of manganese in processing areas.

Background: Accurate prediction of pressure drop across air filters is a key factor in the development of energy-efficient filtration systems for industrial air cleaning. Pressure-drop models such as the Jump-Channel model and Davies-type correlations are commonly used during filter development and material screening to estimate the future pressure drop. However, these models are often derived or validated at media or laboratory scale. Therefore, further research is needed to assess their applicability to full-scale filters under realistic conditions.

Objective: The objective of this study is to evaluate how well models such as Jump-Channel and Davies-Extended pressure-drop models predict steady-state pressure drop in full-scale filters. The study aims to increase understanding of the models’ performance at full scale and quantify deviations between model predictions and experimental measurements. In addition, determine if deviations are systematic or dependent on key operational parameters such as airflow rate, filter geometry, and filter loading state. The overarching goal is to enable more efficient filter development and to evaluate the value of models in testing filtering solutions.

Method: Experimental tests were performed using a full-scale test rig consisting of three parts: (1) a bottom section where oil mist (under realistic load) is introduced, (2) filter housing accommodating filter cassette, and (3) a top section equipped with a fan to drive the airflow. Pressure drop and filter mass were measured for new filters and when the filters had reached steady state. The experimental pressure-drop predictions were compared with predictions using Jump-Channel model and the Davies-Extended model.

Results and Discussion: Preliminary results indicate that the...

The construction of a tunnel is a very demanding discipline of civil engineering. With an average of 5200 km of newly built tunnels each year on over 2300 construction projects it is an important sector of the infrastructure. In addition to obvious hazards for the workers such as blasting work or construction machinery, mineral fine dust also poses a risk to workers’ health. Among these fine dusts, those containing quartz particles smaller than 4 μm are particularly dangerous, as they can enter the lungs and cause diseases such as silicosis or lung cancer.

The research project LUQUAS, which is a consortium of several Austrian companies and universities, is working on the design of a suitable system for mechanical dust suppression using a spray mist system, which uses water droplets to bind the dust particles in the air and therefore forces them to sediment more quickly to the ground. Since tests and measurements on active tunnel construction sites are very complex and difficult to implement, the effectiveness of the use of atomizing nozzles is to be determined by means of laboratory-scale tests and optimal operating parameters.

A dust dispersion unit, which can disperse a defined dust mass flow of the test dusts Carolith (0-0,2) and Sikron SF600 over a longer period, is placed at the front. This is intended to simulate the release of dust during tunnel blasting at the face. The spray mist is generated at a right angle to it using a nozzle spray stand which is operated at different pressures. The results demonstrate that the use of atomizing nozzles in areas with high dust concentrations can contribute to a reduction in airborne matter. The presentation of this topic at FILTECH 2026 will focus on the challenges and solutions for the representative experimental test setup.

This research project aims to contribute to the effective reduction of dust emissions from diffuse sources, including in the areas of bulk material processing, construction and demolition, logistics, ports, waste and recycling management, quarrying and mining, sawmills and the wood industry, and the steel industry.

The aim is to achieve a level of knowledge that will enable the innovative technology of electrostatically assisted wet dust removal to be implemented in industrial practice in the field of dust binding. Companies that emit dust should be enabled to demonstrate the effectiveness of appropriate measures to the authorities....

Particle emissions from combustion engines mainly consist of soot and additives from the lubrication oil. These emissions can be almost fully eliminated by using wall-flow filters in the exhaust aftertreatment system. During regeneration, the organic soot burns away, leaving only ash in the filter channels. The overall structure of the ash agglomerates and their distribution pattern within the channel of the wall-flow filter is influenced by a multitude of different factors. These include, for example, the temperature and velocity during filter regeneration. It is suspected that another influence is water that condenses on the filter surface during a cold start event. As ash consists of partially soluble components, such as CaSO₄, investigating the influence of condensed water on the restructuring and transportation of ash agglomerates in the filter channel will provide further insight into the deposition pattern.

A preexisting wind tunnel is modified to include a vaporizer to vary the relative humidity of the inlet air. An ash substitute can be dispersed into the wind tunnel and deposited in a wall-flow filter sample. Afterwards the filter sample can be subjected to humidifying and drying cycles. Parameters such as pressure drop, temperature, relative humidity and particle concentration can be measured. Changes in the density of the deposited particle layer alongside the filter channel wall can be determined by using an optical microscope. Additionally, structural changes of the agglomerated particles can be microscopically observed under variation of relative humidity using an Environmental Scanning Electron Microscope.

In this work, the first experimental setup will be presented. The different methodological approaches to examine the structural changes of particle agglomerates within the filter channel will be discussed.

Cross-flow filters are central components in exhaust gas aftertreatment systems of modern combustion engines and are used to filter soot and ash particles from the exhaust gas. This causes a layer of particles to form on the filter surface, which increases the pressure drop of the filter. To maintain proper filter operation, the filter is regenerated regularly. The filters are regenerated by oxidizing the deposited particle layer with oxygen at high temperatures (723-873 K) or with nitrogen dioxide at moderate temperatures (523-723 K). Experiments on discontinuous NO₂-assisted regeneration in a wall-flow model filter channel are presented.

For this purpose, a particle layer is deposited on the filter surface using a propane soot generator and exposed to a NO₂-containing (500 ppm NO₂) atmosphere during filter regeneration. The process parameters, such as gas velocity and regeneration temperature are varied. The temporal course of the regeneration, as well as the visible layer break-up and rearrangement of particle structures, are recorded along the length of the channel using a high-speed camera (100-1000 fps).

Solid-state batteries (SSB) differ fundamentally from conventional lithium-ion batteries in that they use solid electrolytes instead of liquid components. In order to efficiently combine the different solids and thereby achieve high electrochemical performance, hetero-agglomeration represents a suitable approach. In particular, the homogeneity and the number of hetero-contacts between different particles have a significant influence on the resulting electrochemical properties, which underlines the central importance of efficient mixing and agglomeration processes.

A jet-based mixing process in a turbulent pipe flow is used to produce cathode materials for SSB with the aim of improving the homogeneity and the electrochemical properties of the battery materials. The starting materials, consisting of the active material lithium iron phosphate (LFP), conductive additive carbon black (CB), and magnesium oxide (MgO), which is used here as a model material for the solid electrolyte lithium indium chloride (LIC), are first broken up and dispersed in the gas phase. The different particles then collide in a turbulent pipe flow, where interactions between the primary particles result in the formation of hetero-agglomerates.

This work focuses on the structural analysis of the hetero-agglomerates produced in the mixing process. The morphological characterization of the particle microstructure was performed using....

Europe´s decision to become climate neutral by 2050 has had an impact on the transport sector through a ban on internal combustion engines from 2035. As a result, expectations of a significant rise in demand for lithium-ion batteries led to plans for gigafactories all across Europe. Laser processing of separator material and other process steps in battery manufacturing cause emissions of health-hazardous contaminants (aromatic compounds, aldehydes, alkenes, halogenated compounds and alkanes), which are also harmful for the product.

Due to competition from Chinese battery manufactures, cost pressure is high and an energy-efficient filtration process is required, that prevents interaction between electrolyte and pollutant as well as mechanical damage of separator foil. As part of a collaborative project between B&S Filtration and ILK Dresden, the intended technological development is a multi-stage filtration process capable of removing corrosive, acid gases (HF, HCl) as well as organic compounds, even at trace concentrations. Its modular design allows for the separation of both current and future pollutants, and certain components are designed to be regenerable.

B&S Filtration is responsible for the development of the filtration process and the filter element, which includes a pre-separator and a pollutant specific multi-layer main adsorption module. The technical evaluation of the filter elements is in the responsibility of the ILK. In this context, a dosing device is implemented to enable a long-term stable generation of multi-component mixtures of model pollutants. The qualitative and quantitative evaluation of the filter elements is carried out using a sequential sampling procedure. Results of the investigations will be presented in more detail in the lecture.

Adsorption processes are increasingly important in modern filtration systems for the removal of pollutants, odors, and chemical contaminants in applications such as water treatment, air purification, carbon capture, and industrial filtration. To support simulation-based analysis and design of adsorption-based filters, a new adsorption modeling capability has been integrated into the GeoDict simulation platform and validated in a joint project with MANN+HUMMEL GmbH, focusing on toluene adsorption on activated carbon.

The methodology couples fluid flow and mass transport simulations to describe adsorption phenomena across multiple length scales. Molecular transport is modeled using an Euler–Lagrange particle-tracing approach, while adsorption equilibria are calculated using established isotherm models, including Langmuir, Toth, and Freundlich. This combined framework enables the prediction of adsorption dynamics and breakthrough curves for a wide range of adsorbates.

Two complementary modeling approaches are implemented within the platform. A tracer-based transport method iteratively solves adsorption equilibria to predict breakthrough behavior in large, non-resolved structures such as cabin air filters or honeycomb geometries. A field-based approach targets smaller, fully resolved microstructures, such as packed beds, where solute transport is represented by a transient concentration field.

For validation, MANN+HUMMEL GmbH provided a µCT scan of a filter medium containing activated carbon. The image data were processed in GeoDict to generate a 3D-representation of the filter structure for adsorption and desorption simulations. Material parameters of the activated carbon, including porosity and tortuosity of the unresolved particles, as well as adsorption isotherms for toluene and corresponding experimental datasets, were also supplied. Based on the experimental conditions, both adsorption and desorption simulations were performed. The tracer-based toluene adsorption simulations showed very good agreement with experimental breakthrough data, while desorption simulations were consistent with physical expectations.

The validated simulation approach enables identification of critical transport and adsorption effects, such as hot spots and poorly utilized regions, and supports systematic optimization of adsorption-based filtration systems. By providing insight into adsorption mechanisms from microstructure to component scale, the approach reduces reliance on extensive experimental prototyping and supports efficient digital development of advanced filtration technologies.

Future work will focus on extending the framework to additional adsorption isotherms, multi-species adsorption, and further improvements in computational efficiency to address emerging challenges in next-generation adsorption-based filtration technologies.

Biochar-based adsorbents have attracted increasing attention as sustainable materials for low-concentration CO₂ capture in air filtration and direct air capture (DAC) applications. Among various biomass resources, bamboo-derived biochar is particularly attractive due to its rapid renewability and favorable carbon framework. However, the effects of chemical activation severity on pore structure evolution and practical CO₂ adsorption performance are not yet fully understood, especially under conditions relevant to air filtration.

In this study, bamboo-derived biochar samples activated under different potassium hydroxide (KOH) conditions were systematically investigated to elucidate the relationship between activation severity, structural evolution, and CO₂ adsorption behavior. Textural and physicochemical properties were characterized using nitrogen adsorption (BET analysis), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). CO₂ adsorption isotherms were measured at ambient temperature to evaluate adsorption performance in the low-pressure range relevant to air-based CO₂ capture.

The results revealed a non-monotonic [...] adsorption performance on activation severity. Moderate activation promoted pore development and enhanced CO₂ uptake, whereas intermediate activation conditions resulted in a temporary decrease in surface area and adsorption performance, likely due to pore blockage or reduced accessibility during structural transition. With further activation, surface area and CO₂ adsorption performance were recovered, indicating the formation of newly accessible pore networks. These structural transitions were qualitatively supported by SEM observations and changes in inorganic residue distribution identified by EDS analysis.

Overall, the findings demonstrate that ...

Neon (Ne) is an essential noble gas used in semiconductor and display manufacturing processes, particularly as a laser source in photolithography and laser-based annealing applications. Due to its extremely low abundance in the atmosphere and chemical inertness, neon is obtained exclusively through air separation processes and requires additional purification before reuse. Recent supply chain disruptions have further underscored the need for efficient, practical neon purification and recycling technologies. Recovered neon typically contains impurity gases such as argon (Ar) and oxygen (O₂), which must be selectively removed to ensure stable process performance. Conventional cryogenic purification methods are energy-intensive and rely on large-scale infrastructure, which motivates the development of alternative, low-energy separation technologies.

In this study, a filter-based direct purification approach using a microporous metal-organic framework (MOF) (size 5-8 Å) was investigated for the selective removal of impurities from neon-containing gas streams. Breakthrough experiments were conducted using a packed column filled with a microporous MOF under continuous gas flow conditions. The outlet gas composition was monitored in real time using a quadrupole mass spectrometer to evaluate the dynamic adsorption behavior of individual gas components. The results demonstrate that [...] selectively adsorbs argon and trace oxygen, while neon exhibits negligible adsorption and passes through the column without delay.

These findings indicate that a [...] enables indirect neon purification by selectively removing impurity gases rather than directly capturing neon. The MOF-based filter system presented in this work offers a promising, low-energy, and scalable solution for noble gas purification and recycling, with potential applications in semiconductor and display manufacturing.

Surface filtration is an established procedure for separating particles from particle-laden gas streams. After an initial depth filtration phase, during which the particles are mainly collected on the fibers inside the filter medium, the main separation of particles is located on the surface of the filter medium and the further accumulating dust cake on the medium surface. This filtration mechanism enables a high collection efficiency of particles for emission reduction or product recovery.

Different surface filter designs, such as bag filters, cartridge filters, and filter panels, are commonly used in industrial filtration processes. The geometry of the filter medium and the filter element can vary depending on the intended application. The use of pleated filter media enables the application of a larger filter media surface in the same installation space, if compared to its flat counterpart.

Pleated filter elements are also applied when space restrictions occur to allow the implementation of the necessary filter media surface area. Nevertheless, the pleating of the filter media can result in problems concerning the stable operating behavior of surface filters.

Existing standards (e.g. DIN ISO 11057, VDI 3926) are commonly used to evaluate and characterize cleanable filter media in a flat, coupon geometry. The findings of these standardized test are often transferred to pleatable filter media and their operating behavior in pleated filter elements without questioning the appropriateness.

This contribution presents an experimental procedure for the direct evaluation of the operating behavior of differently pleated filter media using a test-rig in accordance with DIN ISO 11057, with harmonized experimental conditions (filter media face velocity, raw gas dust concentration and cleaning intensity) applied to each geometry. This direct characterization enables a clear assessment of the influence of filter medium geometry on operating behavior.

Adsorption filters are a key technology for the removal of gaseous pollutants in various applications, including fuel cells, medical technology, and industrial air purification. Pleated filter elements are widely used due to their increased surface area, enabling compact designs with high efficiency. A central metric for their performance evaluation is the breakthrough curve, which describes the adsorption behavior as a function of time and pollutant concentration. However, the experimental determination of breakthrough curves is costly and time-consuming, as it requires prototype manufacturing and extensive test campaigns.

This work addresses the numerical prediction of SO₂ adsorption in pleated filters using CFD simulations. An empirically calibrated mathematical model was implemented in Ansys Fluent to reproduce breakthrough behavior and to investigate the influence of geometrical and operational parameters.

In Figure 1 the results of measurements and simulations are shown at different incoming flow velocities u and different pleat numbers, what correlates with different pleat distances.

The results in Figure 1 demonstrate that [...]. In particular, the effects of pleating on flow distribution and adsorption capacity were quantified, allowing a reliable estimation of filter lifetime. The approach significantly reduces the need for time- and cost-intensive testing and provides an efficient tool for the design and optimization of adsorption filters.

Increasing the number of pleats in dust collection filters is commonly associated with improved filtration performance due to the enlargement of the effective filtration surface area. However, this increase in surface area does not always result in enhanced filtration efficiency or extended filter lifetime. As the pleat number increases, pleat angles become narrower, airflow distribution deteriorates, and pressure drop may rise significantly beyond a certain threshold. This indicates that evaluating filter performance solely based on surface area is insufficient and highlights the necessity of an engineering-based optimization approach.
In this study, the influence of pleat number on the filtration performance of dust collection filters is investigated using an integrated engineering approach combining experimental testing and numerical analysis. Filter samples with identical overall geometry but different pleat numbers are examined using a specially designed test rig. During the experiments, filtration media properties, airflow rate, and dust type are systematically varied, and their effects on pressure drop and filtration efficiency are comparatively analyzed. Throughout the testing process, inlet and outlet dust concentrations are continuously monitored to determine filtration efficiency, while the evolution of pressure drop over time is recorded.
The experimental results are validated by comparing them with theoretical data obtained from Computational Fluid Dynamics (CFD) analyses. CFD simulations are employed to analyze airflow distribution, local velocity profiles, and pressure drop mechanisms for different pleat geometries. Additionally, under regular dust loading conditions, the relationship between initial pressure drop and clogging-induced pressure increase is evaluated to predict filter clogging behavior.
In the advanced stage of the study, an artificial neural network (ANN)-based model is planned to be developed using the experimental data. Considering that artificial intelligence-based approaches are becoming increasingly inevitable in the filtration industry, the proposed ANN model aims to predict pressure drop and filtration performance for new filter geometries and operating conditions. The presented methodology...

Coalescence filters are essential for removing oil mist in compressed air systems. Operating these filters at reduced face velocities offers significant potential for energy savings. Investigations under real operating conditions, particularly at elevated temperatures typical of compressor discharge, are essential to verify whether the potential benefits of lower filter face velocities, such as the reduced energy consumption, are realized in practice. However, most studies have been conducted under laboratory conditions. Preliminary experiments at 80 °C revealed unexpected filter behavior, deviating from theoretical predictions based on the “jump-and-channel” model. These deviations highlight gaps in mechanistic understanding.

This contribution proposes an experimental approach to study coalescence filtration mechanisms across three observation scales: single fibers and fiber arrays (micro), non-woven structures (meso), and full filters (macro). This multi-scale approach has been selected since the macroscopic filter performance results from mechanisms at smaller scales not observable at the filter level. In order to identify how the operating conditions influence the filter behavior, the setup allows for the systematic investigation across the temperature range from 20 °C to 80 °C, with adjustable filtration velocities ranging from 2 to 10 cm/s. A modular filter holder ensures reproducible conditions across all scales within the same filter chamber, which features a glass window enabling optical observation. Specific target parameters such as differential pressure or local saturation are defined in order to characterize the relevant mechanisms at each level.

The proposed approach aims to explain the underlying mechanisms of coalescence filtration by combining the observations from all three scales. Furthermore, it can explain how these mechanisms are affected by reduced face velocities and temperature-induced changes in fluid and media properties, establishing a basis for energy-efficient filter optimization.

Oil mist coalescence filters are essential components in industrial compressed air systems due to their efficient separation of submicron oil droplets from the gas phase. Liquid transport within these multilayer filter systems is governed by complex interactions between airflow, capillary transport, and gravity-driven drainage, which strongly influence pressure loss and separation efficiency during operation. Recent investigations on spatio-temporal drainage in oil mist filters show significant gravitational drainage at the structural interfaces between the support structure and the drainage layer at a moderate filtration velocity of 25 cm/s.

This study presents an experimental methodology to resolve spatially and temporally differentiated oil drainage pathways in multilayer oil mist coalescence filters under realistic operating conditions. A gravimetric online measurement technique is developed to quantify individual drainage flows in real time. The setup combines an additively manufactured filter chamber with defined drainage segmentation and an optical observation system for the rear side of the filter, enabling direct correlation between drainage location, onset time, and pressure loss evolution.

Using this methodology, the influence of filtration velocity (25 and 50 cm/s) and drainage material pore size on oil transport, pressure loss, and separation efficiency for submicron droplets is systematically investigated. The approach allows the relationship between filtration conditions, gravitational drainage behavior, and structural interfaces within the filter to be resolved experimentally.

Fiber-based structures play a crucial role in technical filtration applications. These structures are inherently complex, characterized by randomly oriented fibres with varying diameters and porosities. Accurately modelling particle deposition within such intricate geometries is challenging—not only due to the irregular structure but also because of the computational effort required for mesh generation.

To overcome these limitations, this study introduces an alternative framework that integrates Physics-Informed Neural Networks (PINNs) as flow solvers with Smoothed Particle Hydrodynamics (SPH) for simulating particle interactions within the fibre network. This combined approach allows for the modelling of complex processes such as particle deposition, liquid film formation, and re-entrainment, providing a robust alternative to conventional CFD techniques. PINNs have recently gained significant traction in the fluid mechanics community. Their appeal lies in their unique loss formulation, which embeds governing physical equations (such as the Navier–Stokes equations) and boundary conditions directly into the optimization process without the need for extensive training data.

The SPH method, on the other hand, is a mesh-free CFD technique that represents fluids as discrete particles. To accurately capture the filtration process in complex fibre geometries, this work couples the PINN and SPH methods into an integrated framework. This coupling is crucial for handling dynamic domain changes such as local blockages caused by extensive film deposition. Although initial PINN training can be computationally demanding, subsequent time steps benefit from transfer learning, enabling rapid adaptation to geometric updates (including new film layers on fibres).

This hybrid PINN–SPH framework provides an efficient and scalable approach for simulating droplet deposition in three-dimensional fibre structures. The proposed numerical model has been validated against data from single-fibre filtration experiments. The simulation results for complex multi-fibre configurations are presented and analysed in detail, demonstrating the capability and accuracy of the coupled PINN–SPH approach...

Electret filters use electrostatically charged nonwoven layers to enhance particle separation efficiency. However, this positive electret effect decreases as the particle loading increases. The aim of ioniser-assisted filtration is to significantly enhance the separation efficiency of a conventional filter with low pressure loss, or to achieve the same degree of separation with reduced electrical power consumption.

The approach is based on the ionisation of the air and the subsequent electrical charging of the particles in the electric field of an ioniser. A downstream electric field induces the polarisation of the filter and the separation of the particles. This effect is switchable and persists as long as the ioniser and the electric polarisation field are in operation.

For the optimal design of the ionisation and polarisation unit, a comprehensive CFD model was developed as an extension of the open-source software OpenFOAM. The model takes into account the physical processes in detail, including ionisation, particle charging, and separation in the gas phase, as well as, bipolar charge transport within the solid filter medium. These processes are coupled via the spatially resolved calculation of the electric field.

The model is validated using a combined approach of numerical simulations and experimental investigations. For the experiments, a laboratory test rig has been setup, which allows the investigation of particle charging by ionisation and particle separation due to electrostatic effects on dielectric components. For this purpose, both fibre filter media and plastic grid structures are used.

The use of plastic grid structure keeps the numerical effort manageable and makes it possible to calculate the physical relationships at the microscale and verify them experimentally without having to perform the simulation on a real filter structure...

Numerical simulations are an established tool for investigating the interaction between air flow and the transport and deposition of aerosols in filter nonwovens. The representation of the microstructure of the nonwoven fabric (pore spaces and fibers) in the computational grid makes it possible to assess the filter performance (flow resistance, fractional efficiency, lifetime) and to obtain valuable information for improving the design of the filter material.

Most simulation models assume that the nonwoven can be represented as a porous microstructure formed by individual fibers with (usually) different diameters. In reality, however, a certain proportion of the fibers forms bundles (Figure 1). This effect is process-related (e.g., meltblown process) and cannot be completely avoided. The formation of fiber bundles has a positive effect on the material properties: The bundles improve mechanical stability and increase the air permeability of the nonwoven fabric, since for a given fiber volume fraction, there are larger pore spaces than in the case of a microstructure consisting exclusively of individual fibers. On the other hand, larger pore spaces have a negative effect on filter efficiency.

The present work is devoted to a systematic study of the influence of the presence of fiber bundles on the filter performance of nonwoven media for air filtration. First simulations conducted using GeoDict software reveal, as expected, that the presence of bundles in fibrous structures leads to increased permeability and reduced filtration efficiency in comparison to a structure based on individual fibers.

In the simulated cases, the relative change of permeability varies from a few percent to several tens of percent, depending on bundle size (i.e., the number of agglomerated fibers) and the proportion of bundles within the structure (for a constant overall packing density). However, the impact on filtration efficiency appears to be ...

In this study, numerical simulations based on Computational Fluid Dynamics (CFD) were performed to characterize the thermo-fluid-dynamic behavior of the pulse jet cleaning process in filter bag units. The technical objective was to preliminarily evaluate the feasibility of exploiting the cooling effect of the expanding pulse jet to regulate the temperature of sensor equipment installed at the top of the filter bag collar within the clean air zone. One of the main challenges addressed in this work concerned the development of a simulation strategy capable of providing meaningful engineering indications while ensuring an adequate level of accuracy and an acceptable computational cost. To this end, a two-stage, decoupled computational methodology was proposed. In the first stage, the airflow within the entire purge tube equipped with multiple nozzles was simulated, followed by a more detailed analysis of the flow dynamics in the vicinity of a single filter bag. The fluid dynamic model, based on the compressible Unsteady Reynolds-Averaged Navier–Stokes equations, along with the numerical settings for grid generation and time-step discretization, was adopted from a previous project. Preliminary results yielded useful insights, particularly regarding the optimal positioning of the sensor equipment along the purge tube and the identification of key environmental and process parameters affecting the jet cooling potential.

Nonwoven filter media for aerosol filtration are subject to comprehensive analyses for characterization and optimal design referring to specific applications. Particularly for newly introduced filter media, 3D simulation of the aerosol filtration process for different fiber compositions and states of charge can accelerate the development process and improve the adjustment to specific needs.

In previous studies with the simulation software DNSlab^®, the modeling of 3D fluid flow, electric field, particle transport and deposition in nonwoven was validated by matching measured pressure drops and filtration efficiencies with simulation results. Lacking detailed experimental data on the charge distribution on the fibers surface, various possible surface charge distributions were presumed [Kerner2020].

In the present study, a new innovative nonwoven material is investigated: Lanaco EMP-160 is composed of natural wool and synthetic polymeric co-fibers, both having distinct electrical charge properties. The filter efficiencies are examined in several test series. In the first step, the filter media are discharged, and the filter efficiency is determined for uncharged fibers. In the second step, the untreated and charged filter media are examined. Electronic Force Microscopy (EFM) measurements are performed to gain insight into the surface charge of the fibers. The results of these measurements provide a charge distribution on the fiber surface, which is reproduced in the 3D simulation as shown in Fig. 1.

Filtration processes play an important role in a wide range of environmental and industrial applications, including air purification and water treatment. In view of increasing environmental pollution and rising energy demands, filter systems must offer high separation efficiency at low pressure losses and a long operating life. Although modern filter materials and structures are already cost-effective and widely used, their performance often results from empirical design and incremental improvements. As a consequence, filters may be oversized to ensure adequate separation performance, leading to unnecessary pressure losses and thus increased energy consumption during operation. An application-specific filter design, therefore, offers significant potential for energy savings and performance improvements.

Numerical flow simulations provide valuable insights into the flow behavior within and around filter structures and are increasingly being used to support filter development. However, direct simulation of particle deposition using Lagrange or DEM approaches remains computationally intensive and limits their applicability in iterative design and optimization processes. This is particularly critical when comparing multiple geometries or when integrating deposition-related objectives into gradient-based optimization frameworks. To close this gap, a flow-based surrogate approach has been developed.

The proposed surrogate model is based on local flow and surface metrics that are already available from Eulerian steady-state CFD simulations. Instead of explicitly calculating particle trajectories, the approach evaluates deposition tendencies using physically motivated indicators derived from the interaction between the local flow direction, surface orientation, and flow properties near the wall. This formulation enables a continuous, surface-resolved representation of deposition tendencies and avoids the need for stochastic particle simulation using computationally intensive multiphase models. The most important advantages of this approach include:

• Negligible additional computing costs compared to pure flow simulations
• Local and surface-resolved evaluation of deposition tendencies
• Compatibility with adjoint-based sensitivity analysis
• Suitability for comparative geometry evaluation and design screening

The surrogate approach is demonstrated in a parametric study covering variations in particle size, particle density, flow velocity, and filter fibre diameter. The resulting surrogate trends are systematically compared with particle-resolved Lagrangian deposition results to evaluate the consistency, applicability, and limitations of the approach...

Fine particles dominate the particle number distribution of Arizona dust ISO 12103-1 A2, commonly used for the performance evaluation of fibrous filter media. However, their role in the overall deposit formation process and subsequent filter clogging is not yet fully understood.

In this work, we investigate the influence of the fine particle fraction on the evolution of deposits using a novel three-dimensional hybrid simulation framework, referred to as SEMI-IB. Here, the fluid flow around fiber(s) and deposited particles is solved under steady-state conditions using spatially resolved immersed boundary method (IBM) simulations, while calculating the fluid-particle and particle-particle/fiber interactions during the unsteady deposition phase using one-way-coupled CFD-DEM simulations based on a coarsened and frozen flow-field solution.

Particle deposition on representative filter media segments is studied considering particle systems with and without the fine particle fraction, such that its impact on deposit formation, possible particle rearrangement and onset of clogging can be evaluated. The results are used for the development of a computationally efficient submodel capturing the effect of the fine particle fraction on the dynamic filtration process without resolving its deposition in detail.