VOC outgassing from baked and unbaked ventilation filters

Volatile organic compounds (VOC) outgassing from newly manufactured baked and unbaked ventilation filters were examined using gas chromatography/mass spectrometry following thermodesorption (TD-GC/MS) technique. Filters were tested under both static and dynamic conditions. Under static conditions, the unbaked filter outgassed VOC (0.50 ± 0.18 μg) more than twice as much as the baked filter (0.23 ± 0.15 μg). 2-Propanol and nonanal were the components outgassed from both baked and unbaked filters and 4-piperidinol, 2,2,6,6-tetramethyl-was determined to be the main contaminant outgassed from the unbaked filters. Series of tunnel experiments were conducted by passing highly purified dry air through the filters and taking air samples upstream and downstream the filter. Under dynamic test conditions, the baked filter was not significantly distinguishable from the background with a downstream total VOC concentration increase only by 35.3%, which was almost 9 times lower than that of the unbaked filter (294%). 3-hydroxy-4,6-di-t-butyl-2H-pyran-2-one was the main VOC outgassed from the unbaked filter. In addition, a general trend of decreasing VOC outgassing with time from baked and unbaked filters was observed in both static and dynamic tests. It also suggested that baked filter behaved like a sink for certain VOC and unbaked filters from different batches may outgas different VOC. Overall, bake-out was proved to be an effective way of reducing VOC outgassing from ventilation filters.