ULTRA-FINE PARTICLES AS INDICATORS OF THE GENERATION OF OXIDIZED PRODUCTS ON THE SURFACE OF USED AIR FILTERS

摘要

Ultrafine particle concentrations were measured upstream and downstream of filter samples when the air passing through the filters either did or did not contain ozone. This was done using small-scale test equipment in a low-polluting office with a very low background ozone level. When the airstream contained ozone, the downstream/upstream concentration ratio of ultrafine particles was higher than when the airstream did not contain ozone. It is not anticipated that the filter removes ultrafine particles less efficiently when ozone is present in the airstream. Instead, the fact that the downstream/upstream ratio was higher when ozone was present indicates the creation/growth of ultrafine particles after the air has passed through the filter. Such an observation is consistent with low volatility oxidation products desorbing from the filter and subsequently partitioning between the gas phase and the surface of ultrafine particles that have passed through the filter, including particles that were previously too small (＜ 20 micron diameter) to be detected by the instrument used in these studies.