Efficiency of respirator filters against nano-aerosols under high flow conditions.
Gardner-P; Richardson-A; Rengasamy-S
2nd International Symposium on Nanotechnology and Occupational Health, October 3-6, 2005, Minneapolis, Minnesota. Minneapolis, MN: University of Minnesota, 2005 Oct; :57
Respirators are routinely used in the workplace to protect against a variety of airborne particulate contaminants. The filtration efficiency of particulate respirators are certified by the National Institute for Occupational Safety and Health (NIOSH) at a constant flow rate of 85 L/min using salt and oil test aerosols having a mass median diameter (MMD) of approximately 300 nm. However, measurements of physiological parameters of workers show peak inhalation flow rates for short durations in excess of 400 L/min for certain activities that demand high work loads. This study investigated the respirator filter efficiency against nano-aerosols (20 to100 nm MMD), which are potential particulate exposure hazards associated with nanotechnology, and larger size aerosol particles (MMD >100 nm) produced in traditional industrial workplace settings. The filtration efficiencies of NIOSH-approved P100 and N95 particulate respirator filtering facepiece masks and cartridge filters were measured at high volumetric and peak flow rates. Four cyclic flow conditions (40, 85, 115, and 135 L/min minute volume) with peak flows up to 430 L/min and three constant flow rates (85, 270, and 360 L/min) were evaluated. As expected, aerosol penetration was found to increase with increased cyclic and constant flow rate. The magnitude and significance of this increase was dependent on the specific filter type and design. The most penetrating particle size was generally between 100 and 200 nm for the P100 cartridge filters and 50 and 100 nm for the N95 cartridge filters and all filtering facepiece masks. In general, the filters met the penetration requirements for N95 and P100 filters for all particle sizes tested at a constant flow of 85 L/min. However, nano-aerosol penetrations in excess of 0.03 % and 5.0 % for the P100 and N95 filters, respectively, were observed at constant and cyclic flow conditions above 85 L/min. Comparison of the penetrations measured under cyclic and constant flow indicates that the mean and peak inhalation flow rates are important parameters to consider when evaluating filtration performance. For the P100 and N95 cartridge filters, similar penetrations were measured under constant and cyclic flow if the constant flow was equivalent to the mean inhalation flow rate. The penetrations measured at constant flow rates equivalent to the peak inhalation flow under cyclic flow conditions tended to provide a more conservative estimate of filter performance.
Respirators; Respiration; Filters; Filtration; Aerosols; Airborne-particles; Particulates; Exposure-levels; Exposure-assessment; Nanotechnology
National Personal Protective Technology Laboratory, NIOSH, 626 Cochrans Mill Road, Pittsburgh, PA 15236
Abstract; Conference/Symposia Proceedings
2nd International Symposium on Nanotechnology and Occupational Health, October 3-6, 2005, Minneapolis, Minnesota