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.