A quantitative assessment of the total inward leakage of NaCl aerosol representing submicron size bioaerosol through N95 filtering facepiece respirators and surgical masks.
Rengasamy S; Eimer BC; Szalajda J
J Occup Environ Hyg 2014 Jun; 11(6):388-396
Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. The contribution of filter penetration and faceseal leakage to total inward leakage (TIL) of submicron size bioaerosols is not well studied. To address this issue, TIL values for two N95 filtering facepiece respirator (FFR) models and two surgical mask (SM) models sealed to a manikin were measured at 8 L and 40 L breathing minute volumes with different artificial leak sizes. TIL values for different size (20-800 nm, electrical mobility diameter) NaCl particles representing submicron size bioaerosols were measured using a scanning mobility particle sizer. Efficiency of filtering devices was assessed by measuring the penetration against NaCl aerosol similar to the method used for NIOSH particulate filter certification. Results showed that the most penetrating particle size (MPPS) was approximately 45 nm for both N95 FFR models and one of the two SM models, and approximately 350 nm for the other SM model at sealed condition with no leaks as well as with different leak sizes. TIL values increased with increasing leak sizes and breathing minute volumes. Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher efficiency FFRs may offer higher protection against submicron size bioaerosols.
Respirators; Respiratory-equipment; Personal-protective-equipment; Leak-detectors; Leak-prevention; Quality-control; Quantitative-analysis; Air-purifying-respirators; Face-masks; Failure-analysis; Air-filters; Aerosol-particles; Aerosols; Filters; Laboratory-testing; Breathing; Sodium-compounds; Chlorides; Equipment-reliability; Air-flow; Infection-control;
Author Keywords: NaCl aerosol; infectious bioaerosol; filter penetration; face seal leakage; total inward leakage; N95 filtering facepiece respirator; surgical mask
Samy Rengasamy, National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 18070, Pittsburgh, PA 15236, USA
Journal of Occupational and Environmental Hygiene