In recent years cabin air combination filters for cars have become increasingly popular. They are designed to eliminate both particles and gaseous pollutants from the cabin air. The removal of noxious gases takes place through adsorption by a layer of activated charcoal granules. According to German and international standards these cabin air filters are tested at a temperature of 23 degreesC and 50% relative humidity. But in practice they are exposed to a wider range of temperatures, humidity and input concentrations. These parameters have a strong effect on adsorption, so they also influence the adsorption capacity of cabin air filters. Experiments on a filter test stand at the Department of Chemical Engineering, University of Duisburg, with varying temperature, relative humidity and input concentrations show that adsorption capacity is significantly reduced at higher temperatures or higher relative humidity. When the temperature or the relative humidity rises or when the input concentration falls desorption of previously adsorbed pollutants occurs.