How Protective Are Respirator Assigned Protection Factors: An Uncertainty Analysis

Abstract

This investigation evaluated the risk of overexposure for a selected assigned protection factor by performing Monte Carlo simulations. A model was constructed to assess respirator performance by calculating the concentration inside the respirator. Estimates of the factors that affect respirator performance were described as distributions. The distributions used a worst case estimate for concentration in the workplace, the worst case for respirator performance (the fifth percentile person), and the worst case for exhalation valve leakage. A Monte Carlo analysis then provided estimates of the percentage of time that concentration inside the respirator exceeded the occupational exposure limit (OEL). For a half-facepiece respirator with an APF of 10, the calculations indicated a low risk of being exposed above an OEL, with mean exposures being controlled well below an OEL.

Exposure to Manufactured Nanostructured Particles in an Industrial Pilot Plant

“…Mask efficiencies to various airborne inert particles have been investigated in laboratories as well as under workplace conditions (Nelson et al, 2000;Bidwell and Janssen, 2004;Lee et al, 2005;Kim et al, 2007;Eninger et al, 2008). However, the number of studies regarding natural and engineered nanoparticles is limited.…”

Research on Regularities of Cyclic Air Motion through a Respirator Filter

“…with initial conditions m(h, 0) = 1, m(0, t ) = m1, c(0, t ) = 1. Expression (17), taking into account the independence of the mixed derivative from the differentiation order, makes it possible to obtain an equation for calculating the amount of settled dust on the fibres, which changes with the dust sediment accumulation:…”

“…Currently, theoretical functional connections are known which allow the pressure drop in dust respirators to be defined; these were obtained based on constant air velocity [14][15][16][17][18]. Existing design models of respirator filters do not take into account the cyclicity of the process of a user's breathing when performing production activities-this includes the movement of some volume of air from the atmosphere into their lungs and then back, which requires the use of non-stationary filtering theory, which takes into account the movement of alternating air flow through the filter.…”

Evaluation of the rationale for concurrent use of N95 filtering facepiece respirators with loose-fitting powered air-purifying respirators during aerosol-generating medical procedures

“…22,23 APFs are based on laboratory and workplace studies that measure the ratio of the ambient contaminant concentration to the contaminant concentration inside a respirator and are used for selecting what type of respirator to employ in a given situation. 24 Use of a respirator with an APF greater than the calculated hazard risk (ie, ambient concentration of a contaminant O established permissible exposure limit) generally assumes that the exposure inside the respirator will be less than the exposure limit. 24 However, it is important to recognize that, as opposed to particulates and chemicals, governmental regulatory agencies have not established safe exposure levels for biological aerosols; thus, there is no assurance that any respirator will completely eliminate the inhalation of pathogenic microorganisms.…”

“…24 Use of a respirator with an APF greater than the calculated hazard risk (ie, ambient concentration of a contaminant O established permissible exposure limit) generally assumes that the exposure inside the respirator will be less than the exposure limit. 24 However, it is important to recognize that, as opposed to particulates and chemicals, governmental regulatory agencies have not established safe exposure levels for biological aerosols; thus, there is no assurance that any respirator will completely eliminate the inhalation of pathogenic microorganisms. Nonetheless, it is assumed that the higher the APF, the more protection afforded the wearer.…”