Hence many of the variables that can adversely affect protection actually provided to workers in typical respirator programs are not reflected in WPF studies.
In 1985, the AIHA Respirator Technical Committee, chaired by H. P. Guy, prepared a "consensus terminology" for respirator performance in consultation with the principals from Los Alamos National Laboratory and NIOSH.[1] The Guy Committee
recommended that the terminology be published in the AIHA Journal and ultimately
adopted for manuscripts submitted to the Journal. The Guy Committee provided the
following APF definition:
The minimum expected workplace protection level of respiratory protection that would be provid
ed by a properly functioning respirator or class of respirators, to a stated percentage of properly
fitted and trained users. The maximum use concentration for a respirator is generally deter-
mined by multiplying a contaminant's exposure limit by the protection factor assigned to the
respirator.
72
The Guy Committee also recommended the following definition for workplace protec-
tion factors:
A measure of the protection provided in the workplace, under the conditions of the workplace, by
a properly selected, fit tested and functioning respirator when correctly worn and used. It is
defined as the workplace contaminant concentration which the user would inhale if he were not
wearing the respirator (Co) divided by the workplace contaminant concentration inside the respi-
rator facepiece (C₁). Both Co and C, are determined from samples taken simultaneously, only
while the respirator is properly worn and used during normal work activities. 73
Regarding NIOSH's 1987 recommended APF values," NIOSH stated:
When WPF data existed, NIOSH utilized the point estimate equation proposed by Myers et al.
[13] to help establish the APF's recommended in the decision logic. The point estimate equation
is as follows...
72Tbid., p. B-22. 73Tbid. 74 NIOSH Respirator Decision Logic, DHHS (NIOSH) Publication # 87-108, Cincinnati, OH (May, 1987),
Tables 1-3, pp. 2-4, 13-18, and 27-29.
- ↑ Guy, H. P.: Letter to the Editor Respirator Performance Technology, Am. Ind. Hyg. Assoc. J. 46(5):B-22 to B-24 (1985).
