"Worst case" aerosol testing parameters: II. Efficiency dependence of commercial respirator filters on humidity pretreatment.
Previous studies have shown that relative humidity has a degrading effect on the performance of commercially available particulate air-purifying respirator filters. That degradation results from a reduction of charge within the filter. This study was done to evaluate the time-dependent effects of relative humidity pretreatment and the reduction of charge on filter penetration against a most penetrating, "worst case" aerosol challenge. Filters of the dust and mist; dust, fume, and mist; paint, lacquer, and enamel mist; and high efficiency types were tested after being pretreated in an environment of 38 degrees C and 85% relative humidity for periods up to 42 days. After various intervals of pretreatment (1, 7, 14, 28, and 42 days), the filters were tested against neutralized worst-case sodium chloride (NaCl) and dioctyl phthalate (DOP) aerosols for percent penetration. The results showed a drop in filter efficiency of approximately 2%-6% depending on preconditioning time, except for the high efficiency filters tested which showed no detectable change.
Moyer
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National Institute for Occupational Safety and Health, Division of Safety Research, Morgantown, WV 26505-2888.
Stevens
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GA
D000336:Aerosols; D004051:Diethylhexyl Phthalate; D004781:Environmental Exposure; D005374:Filtration / Q000295:instrumentation* / Q000592:standards; D006813:Humidity; D011482:Protective Devices / Q000592:standards*; D012134:Respiratory Protective Devices / Q000592:standards*; D012965:Sodium Chloride; D013997:Time Factors
D000336:Aerosols; D012965:Sodium Chloride; D004051:Diethylhexyl Phthalate