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Document ID (ISN)111727
CIS number 11-0402
ISSN - Serial title 1545-9624 - Journal of Occupational and Environmental Hygiene
Year 2009
Convention or series no.
Author(s) Grinshpun S.A., Haruta H., Eninger R.M., Reponen T., McKay R.T., Lee S.A.
Title Performance of an N95 filtering facepiece particulate respirator and a surgical mask during human breathing: Two pathways for particle penetration
Bibliographic information Oct. 2009, Vol.6, p.593-603. Illus. 20 ref.
Abstract The protection level offered by filtering facepiece particulate respirators and face masks is defined by the percentage of ambient particles penetrating inside the protection device. There are two penetration pathways: through face-seal leakage and through the filter medium. This study aimed at differentiating the contributions of these two pathways for particles in the size range of 0.03-1μm under actual breathing conditions. One N95 filtering facepiece respirator and one surgical mask commonly used in health care environments were tested on 25 subjects as the subjects performed conventional fit test exercises. The respirator and the mask were also tested with breathing manikins that precisely mimicked the pre-recorded breathing patterns of the tested subjects. The penetration data obtained in the human subject- and manikin-based tests were compared for different particle sizes and breathing patterns. Overall, 5250 particle size- and exercise-specific penetration values were determined. For each value, the face-seal leakage-to-filter ratio was calculated to quantify the relative contributions of the two penetration pathways. The number of particles penetrating through the face-seal leakage of the tested respirator/mask far exceeded the number of those penetrating through the filter medium. For the N95 respirator, the excess was by an order of magnitude and significantly increased with an increase in particle size: approximately 7-fold greater for 0.04μm, approximately 10-fold for 0.1μm, and approximately 20-fold for 1μm. For the surgical mask, the face-seal leakage-to-filter ratio ranged from 4.8 to 5.8 and was not significantly affected by the particle size for the tested sub-micron fraction. Facial/body movement had a pronounced effect on the relative contribution of the two penetration pathways. Breathing intensity and facial dimensions showed some limited influence. Because most of the penetrated particles entered through the face-seal, the priority in respirator/mask development should be shifted from improving the efficiency of the filter medium to establishing a better fit that would eliminate or minimize face-seal leakage.
Descriptors (primary) filtration efficiency; particulate removing respirators; facepieces
Descriptors (secondary) anthropometry; equipment testing; comparative study
Document type D - Periodical articles
Subject(s) Personal protection
Broad subject area(s) Chemical safety
Browse category(ies) Respiratory protection