Sorption material in gas cleaning units that serve occupational health and safety must be changed at an appropriate early stage. The instructions from the professional associations stipulate that driver's cabs must have an appropriately equipped ventilation system when used in contaminated areas. However, the standards for the sorption filter specified in the document only contain the type of filter test and no recommendations for the duration of use. The research project at the ILK Dresden aims to develop a sensor system for the safe monitoring of the operating status of a sorption device for the separation of gaseous substances from air. The sensor we develop will convert the loading status of the sorption agent into an electrical signal so that a warning message can be issued to the user or the system control when a threshold value is reached. The measurement is carried out via the electrical capacitance at a frequency and a specific measuring voltage. Capacitance/voltage converters are used, which enable a simple evaluation to be carried out. Such ICs (interdigital circuits) cost between 10 and 30 €. The evaluation unit includes the sensor unit, so they are reusable. The price also allows several sensor elements to be queried in the filter element, which means that the resolution of the adsorption front can be mapped more precisely. It is essential to record the moisture, as the water retention dominates the loading of the sorbent. This observation is confirmed by measurements carried out at the ILK Dresden on pollutant filters actually used. The filter elements used were exposed to 70% humidity and the test gas cyclohexane at the nominal volume flow. One filter element showed an immediate breakthrough with the simultaneous release of moisture into the clean gas. The sorbent is evidently saturated with water. Therefore, sensor elements for temperature and humidity are placed up and downstream of the filter. We prefer printed electronics for these sensors. Results will be discussed...