Evaluation of the filtration performance of 21 N95 filtering face piece respirators after prolonged storage.
BACKGROUND
Organizations are stockpiling respirators to prepare for an influenza pandemic. To understand better the effects of prolonged storage, this investigation evaluated the filtration efficiency of 21 different models of National Institute for Occupational Safety and Health (NIOSH)-certified disposable N95 filtering face piece respirators. These respirators had been stored in their original packaging for a period of at least 6 years in research laboratories and dry warehouse facilities, ranging in temperature between 15 degrees C and 32 degrees C and relative humidity between 20% and 80%.


METHODS
Filter penetration was measured using an abbreviated version of the NIOSH respirator certification test incorporating a polydisperse sodium chloride aerosol at 85 L/min.


RESULTS
Of the 21 respirator models tested, 19 models had both average penetration results of less than 5%. Mean initial penetration values ranged from 0.39% to 5.83%, whereas mean maximum penetration values ranged from 0.95% to 5.83%. There did not appear to be any correlation between the length of storage and failure to pass the filtration test.


CONCLUSIONS
Results indicate that most N95 filtering face piece respirators stored for up to 10 years at warehouse conditions will likely have expected levels of filtration performance and that the degree of filtration efficiency degradation is likely model specific.
Viscusi
Dennis J
DJ
National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Pittsburgh, PA.
Bergman
Mike
M
EG&G Technical Services, Inc, Pittsburgh, PA.
Sinkule
Edward
E
National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Pittsburgh, PA.
Shaffer
Ronald E
RE
National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Pittsburgh, PA. Electronic address: RShaffer@cdc.gov.
D000336:Aerosols; D019544:Equipment Failure Analysis; D005374:Filtration / Q000295:instrumentation / Q000592:standards; D006801:Humans; D019570:Inhalation Exposure / Q000517:prevention & control*; D009314:National Institute for Occupational Safety and Health, U.S. / Q000592:standards; D010316:Particle Size; D012134:Respiratory Protective Devices / Q000592:standards*; D012965:Sodium Chloride; D013997:Time Factors; D014481:United States
D000336:Aerosols; D012965:Sodium Chloride