Sensory source strength of used ventilation filters

A two-years old filter was placed in a ventilation system recirculating the air in an experimental space. Via glass tubes air was extracted to an adjacent room to allow a panel to evaluate the sensory load after facial exposure, without entering the space. The sensory pollution load of the filter determined from full exposure was approximately 7 times lower than when determined after facial exposure. Even though, used filters may still be important sources of indoor air pollution.