Initial studies of oxidation processes on filter surfaces and their impack on perceived air quality

Ozone concentrations were monitored up- and downstream of used filter samples at airflows of 1.0 and 0.2 L s-1. The ozone concentration in the air upstream of the filters was ~75 ppb, while the concentration downstream of the filter was initially ~ 35% lower at 1 L s-1 and ~ 55% lower at 0.2 L s-1. Within an hour the removal efficiency had decreased to roughly 5% at 1 L s-1 and 10% at 0.2 L s-1.

These filter samples were then placed in either nitrogen or ambient air for 48 hours. Afterwards it was found that there was partial regeneration of the filter¿s ozone removal capabilities. In companion studies, human subjects assessed air passing through various filter samples. This occurred when samples were first placed in the test rig (each of 3 filters equivalent); immediately after the samples had sat for 48 hours in ozone, nitrogen or air (ozone-treated worse than air-treated worse than nitrogen-treated); and after ambient air had passed through the ¿treated¿ filters for 2 hours.

In the last case all filters were more acceptable than they had been right after the 48-hour treatments. However, the ozonized filter was still the most polluting of the three.