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Probability of overexposure and adequacy of the assigned protection factor for half-facepiece respirators.

Zhuang Z; Myers W
American Industrial Hygiene Conference and Exposition, May 9-15, 1998, Atlanta, Georgia. Fairfax, VA: American Industrial Hygiene Association, 1998 May; :60-61
A number of field studies have been conducted over the last 10-13 years to evaluate the worker protection provided by negative pressure, half-facepiece respirators. Protection was assessed by workplace protection factors (WPF). The appropriateness of the assigned protection factor (APF) (or negative pressure half-mask respirators has generally been evaluated based on the fifth percentile estimate of a WPF distribution. No evaluation has been based on the comparison of in-facepiece concentration and an exposure standard. A new approach based on probability of overexposure was developed to use the combined WPF data published in peer-reviewed journals to evaluate the appropriateness of the APF for half-facepiece respirators. The new approach first utilized a graphical representation of WPF data and hazard ratios (ambient concentration divided by permissible exposure limit). The adequacy of the APF was then evaluated from binomial statistics based on the number of successes (no overexposure) and failures (overexposure). In the studies reviewed, the probability of overexposure occurring during a wearing period for workers wearing half-facepiece respirators represented, was 0.5%, with a 95% confidence interval of 0.01 to 2.7%. If we consider 50% in-facepiece sampling errors, the probability of overexposure was 29% with a 95% confidence interval of 1.1 to 6.3%. Based on this analysis, our professional judgment is that the current APF of 10 for half-face-piece respirators is appropriate.
Respirators; Respiratory-equipment; Face-masks; Air-purifying-respirators; Anthropometry; Personal-protective-equipment; Performance-capability; Health-protection; Testing-equipment; Exposure-assessment; Exposure-levels; Exposure-limits; Statistical-analysis; Permissible-concentration-limits; Hazards
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American Industrial Hygiene Conference and Exposition, May 9-15, 1998, Atlanta, Georgia
Page last reviewed: April 8, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division