Investigations on the survival time of outdoor microorganisms on air filters.

Outdoor microorganism survival on air filters was examined in 16-day field investigations. Using a mobile filter testing device, samples of fiberglass pocket filters (filter class F7) were ventilated with outdoor air, and their microorganism contents were determined at 1, 2, 4, 8 and 16-day intervals. The results showed a mean survival time of microorganisms deposited on the air filters of 1 to 3 days.