Determination of inspiratory pressures and flow rates for work rate-dependent quantitative respirator fit testing.
Crutchfield-CD; Pham-TK; Ert-MD
Appl Occup Environ Hyg 1993 Feb; 8(2):103-107
The use of inspiratory pressures (IP) and flow rates (FR) for assessing leakage in quantitative respirator fit testing was discussed. The controlled negative pressure (CNP) fit test was used. A test population of 30 adult volunteers were fitted with appropriately sized (small, medium, or large) half masks or full face respirators. A minimum fit factor of 100 measured with a CNP fit test system was used as criterion for an acceptable fit. Three 5 minute test cycles with bicycle ergometry and low, medium, and high breathing resistances were recorded. IP and FR were measured during the last minute of each work cycle. Results showed that intrasubject IP variations ranged from 5 to 12%, while FR varied from 4 to 10%. Intersubject variations in IP and FR were 17.4% and 20.1%, respectively. A three way analysis of variance (ANOVA) using work rate, cartridge resistance and gender showed highly significant differences in IP and FR with the first two factors. Gender significantly affected IP only at lower work rates, but affected FR at both high and low work rates. A similar ANOVA with work rate, cartridge resistance and mask type showed that the mask type affected IP and FR. Full face IP were higher than half mask pressures at all work rates and levels of cartridge resistance. These were more marked at higher work rates (about 25% increase). A respirator dead space effect was evident with both IP and FR data for the fullface respirators. Increased tidal volumes associated with this larger dead space played a role in increasing average IP with the full face respirators. The authors conclude that IP and FR can be used to measure leakage rates in the conventional form of a CNP fit factor.
NIOSH-Publication; NIOSH-Grant; Training; Ergonomics; Sex-factors; Face-masks; Physical-exercise; Industrial-exposures; Respiratory-protective-equipment; Industrial-hygiene
Family and Community Medicine University of Arizona Acosh Tucson, Ariz 85724
Applied Occupational and Environmental Hygiene
University of Arizona, Tucson, Arizona