Observations on Electrostatic Effects in a Filter Test System

摘要

The filter test system FTS 400 was used to examine a variety of filter papers, using sodium chloride and dioctylphthalate as aerosols challenges. In nearly every case of minimum in penetration was observed at particle size in the vicinity of 0.02 micrometers. In the same region NaC1 particles (but not DOP droplets) exhibited substantial in-line losses which could affect measured penetration results. Introduction of a radioactive neutralizer which removes most of the particle charge greatly reduced line losses. The effect of introducing the neutralizer on penetration was studied, using several types of filter paper. Conventional filter papers showed slight increase in penetration over the size range up to 0.3 micrometers. With electrets, which depend on electrical attraction for their effectiveness, introduction of a neutralizer increased penetration in the same range by several orders of magnitude.