Editing Respirator (section)

==== Respirator risk modelling ====
[[Respirator assigned protection factors|Assigned protection factors]] (APF) are predicated on the assumption that users are trained in the use of their respirators, and that ''100%'' of users exceed the APF.<ref>"NIOSH has concluded that APFS based on APF definitions from Myers et al. and the Guy Committee are derived from WPF data that were obtained after each test subject has been properly fitted and trained"... {{harvnb|NIOSH|1992|p=34}}</ref> This "simulated workplace protection factor" (SWPF) was said to be problematic:
{{blockquote|By inference, these data are equally at odds with the protection factors established by OSHA for various types of respirator, which were based on QNFT [quantitative fit testing] data obtained by the [[Los Alamos National Laboratory]] in the 1970s. Until recently, the SWPFs gathered during QNFT were more or less assumed to translate directly into the protection afforded by a particular respirator, or class of respirators, while worn in the workplace.{{break}}{{break}}
Apparently this is now a questionable assumption which has thrown the entire concept of fit testing into doubt.<ref name="openforum">Quote from: {{citation| title=Open Forum: Respirator Testing-Old Values |date= May 1989 |publisher=Ind. Safety and Hyg. News}}</ref>}}
The ideal assumption of ''all'' respirator users exceeding the APF is termed the ''zero control failure rate'' by NIOSH. The term ''control failure rate'' here refers to the number of respirator users, per 100 users, that fail to reach the APF.<ref name="NIOSHp52">{{harvnb|NIOSH|1992|p=52}}</ref> The risk of user error affecting the ''failure rate'', and the studies quantifying it, was, according to NIOSH, akin to the study of [[Comparison of birth control methods|contraception failure rates]].<ref>{{harvnb|NIOSH|1992|p=51}}</ref> 

This is despite there being a "reasonable expectation, of both purchasers and users, [that] ''none'' of the users will receive less protection than the class APF (when the masks are properly selected, fit tested by the employer, and properly worn by the users)". NIOSH expands on the methods for measuring this error in Chapter 7 of the draft report.<ref name="NIOSHp52" />