Retention of sulfur dioxide by nylon filters

Based on laboratory studies, recovery efficiencies of sulfur dioxide (SO2) were determined for nylon filters. The nylon filters used in these experiments were found to retain SO2. A relatively uniform amount (1.7%) was recoverable from each nylon filter, independent of relative humidity. An appreciable portion of SO2 was unrecoverable, and this increased from 5 to 16% as the RH increased from 28 to 49%. This unrecoverable SO2 may account for previous reports of a low bias for SO2 determinations employing filter packs using nylon filters. Additional characterization of nylon filters is recommended prior to their future deployment as an integrative sampling medium for ambient air.