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

Ozone concentrations were monitored up- and downstream of used filter samples at airflowsof 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% at1 l s- 1 and 10% at 0.2 l s- 1. These filter samples were then placed in either nitrogen or ambientair for 48 h. Afterwards it was found that there was partial regeneration of the filters ozoneremoval capabilities. In companion studies, human subjects assessed air passing throughvarious filter samples. This occurred when samples were first placed in the test rig (each ofthree filters equivalent); immediately after the samples had sat for 48 h in ozone, nitrogen orair (ozone-treated worse than air-treated worse than nitrogen-treated); and after ambient airhad passed through the treated filters for 2 h. In the last case all filters were more acceptablethan they had been right after the 48-h treatments. However, the ozonized filter was still themost polluting of the three.