THE ASSIGNED PROTECTION FACTOR OF 10 FOR HALF-MASK RESPIRATORS

A number of researchers have published or presented papers on workplac e protection factor (WPF) studies involving half-mask respirators. Ind ividually, each study contains a relatively small amount of data, gene rally less than 25 data points for any single respirator. Because of t he small amount of data, any attempt to quantify the result statistica lly does not provide useful information on the low end of the distribu tion of WPFs. Several studies on half-mask respirators were combined t o yield a data set with 390 observations. Of these WPF data, 1.5% were less than 10, the best estimate of the 5th percentile was 13, with a 95% confidence interval of 10 to 18. Differences between the mean WPF based on the type of filter were found, but no difference was found be tween the mean performance of elastomeric and disposable respirators e quipped with dust/mist and dust/fume/mist filters.