Performance of Dust Respirators with Facial Seal Leaks: II. Predictive Model

Abstract

A performance model for half-mask and single-use respirators is presented. It represents a possible alternative to field measurements of respirator performance. Experimental data on filter and leak performance given in Part I were used to develop a model that allows one to predict 1) the overall respirator penetration as a function of particle size for any work rate and 2) overall total mass penetration for any work rate and exposure aerosol-size distribution for a known respirator filter and facial seal leak condition. A simplified method based on general regression equations is presented that allows one to estimate these quantities based on QNFT (quantitative fit testing) measurements and a knowledge of the exposure aerosol-size distribution. Example calculations are given for a situation in which QNFT gives a fit factor of 50 for a half-mask with dust, fume and mist filter cartridges, but predicted protection factors for various use conditions range from 20 to 81 depending on exposure particle-size distribution and work rate of the wearer.

Penetration of nanoparticles through fibrous filters perforated with defined pinholes

“…Under these circumstances, what would be the filtration efficiency with respect to nanoparticles? Past research on particle penetration through a bypass route formed by a leak within the filter has only really dealt with micronic and submicronic particles (Chen, Ruuskanen, Pilacinski, & Willeke, 1990;Hinds & Bellin, 1987;Hinds & Kraske, 1987;Vaughan, Tierney, & Brown, 1994;Weber et al, 1993), whose behaviour is very different to that of nanoparticles travelling through a capillary. In the case of nanoparticles, could diffusion within the leak be the cause of their higher collection efficiency than for larger particles?…”

Effect of Particle Size on the Performance of an N95 Filtering Facepiece Respirator and a Surgical Mask at Various Breathing Conditions

“…The efficiency of respirator filter media has been assessed in several previous studies by measuring the aerosol concentration inside and outside of the FFR/SM while it was sealed to a manikin headform using constant or cyclic breathing flow (Bałazy et al 2006b; Cho et al 2010b; He et al 2013d; Rengasamy and Eimer 2011; Richardson et al 2007). To simulate faceseal leakage, artificially created slit-like or circular leaks have been commonly used in manikin-based respiratory protection research (Chen and Willeke 1992; Hinds and Bellin 1987; Myers et al 1991; Rengasamy and Eimer 2011). The limitation of most of the previous manikin-based faceseal leakage studies was that the headforms had rigid surfaces, which were unable to simulate the characteristics of the human skin.…”

Performance of a Full Facepiece, Air-Purifying Respirator Against Lead Aerosols in a Workplace Environment

“…(17)(18)(19) Some investigators have suggested that this phenomenon might cause the WPF to increase with increased particle size because particles larger than a few micrometers are less likely to penetrate the faceseal than submicrometer particles. (20,21) However, Wallis et al (21) also noted that their data suggested that some activities could cause short duration "gross leaks." Myers et al (6) used electron microscopy to demonstrate that particles ≥ 10 μm are found on C i WPF samples, further refuting the suggestion that respirator faceseal leaks are a fixed size.…”