Do filters pollute or clean the air?

The contribution of new and used fine bagfilters to indoor air pollution has been determined in a laboratory study by a trained panel as well as by TVOC measurements. The used filters were all taken out of air handling systems which run with full outdoor air supply. The time that a used filter had been situated in the ventilation system until it was taken out and was studied in the laboratory varied from two to ten months. The new filters did not pollute significantly in comparison to the used filters. However, all used filters polluted the air instead of cleaning it.