subsequent determination of APFs. These are presented in Table L of this evaluation.
It is also important to understand how APFs are used in respirator selection in order to appreciate both their significance and limitations. A simplified version of this information is given in Table M of this evaluation. Respirator selection and use activities are regulated by OSHA (under 29 CFR 1910.134) and other Federal agencies.[1]
Table P presents recommended APFs for various respirator types (classes), face-
pieces, and certification performance tests (i.e., 30 CFR Part 11). APFs can be con-
sidered to be potential "effectiveness" or "protection" ratings. They reflect the fact
that different types of respirators are capable of providing different degrees of protec-
tion to wearers. Differences between potential protection values (APFS) afforded by
different respirator types can be quite substantial.
Step 4 of Table M in this evaluation summarizes how APFs are used in respirator
selection. Possible low levels of user protection exhibited by devices with lower APFs
must be recognized and considered by purchasers and users when selecting and us-
ing NIOSH-certified respirators. Hence valid APFs are essential for correct respira-
tor selection.
Most respirator evaluation studies that will be discussed later in this evalua.
tion 35 have measured respirator performance after the test subjects have gone
through Steps 1 through 7 shown in Table M of this evaluation. However there are
numerous factors that can affect the protection levels exhibited by respirators. With
regard to the determinant factors affecting protection levels provided by respirators,
Galvin et al. have stated:
The protection afforded by an air-purifying respirator is determined by two major factors. One is
the fit of the respirator around the face seal [face-seal leakage] and the second is the efficiency of
the cartridge in removing the contaminant from the airstream [filter leakage]. Fit is influenced
by the ability of the respirator to conform to individual facial structure and to maintain the facial
seal during work activities.
35For example, refer to discussion presented in this evaluation under Evaluation of Face-Seal Leakage
Results from Nine Studies of Non-Powered, Air Purifying Halfmasks.
36Galvin, K., S. Selvin, and R. C. Spear: Variability in Protection Afforded by Half-Mask Respirators
Against Styrene Exposure in the Field, Am. Ind. Hyg. Assoc. J. 51:625-639 (1990), p. 625.
- ↑ Refer to discussion presented in this evaluation under Regulatory APFs in NIOSH and Other Federal Agencies.
