DEVELOPMENT OF A DICHOTOMOUS-FLOW QUANTITATIVE FIT TEST FOR HALF-MASKAND FULL-FACEPIECE RESPIRATORS

A new method to quantitate the fit of elastomeric half-mask and full-f acepiece air-purifying respirators was developed. In this method the t wo flows, cartridge flow and leak flow, are separate. The air-purifyin g cartridges of the respirator are attached to a reference respirator. A selected flow, equivalent to the inhalation flow of the wearer is d rawn through the cartridge pair. A feedback system consisting of a pre ssure controller and a control valve is used to set the pressure drop in the mask on the subject's face equal to the pressure drop in the re ference mask. The faceseal leak flow is measured while the subject hol ds his or her breath for a short period of time. The ratio of total fl ow (cartridge flow + leak flow) to leak flow is a measure of fit and i s defined as the flow fit factor. Aerosol fit factors and flow fit fac tors were determined using sampling probes in three mask locations: to p, center, and bottom. A Kruskal-Wallis test showed that aerosol fit f actors obtained from the three locations were significantly different from each other (p = 0.0001) while the corresponding flow fit factors were not. Aerosol fit factors obtained with the center probe had the l east variability. The coefficient of variation in aerosol fit factors ranged from 5.4% for the center probe to 19%for the bottom probe; the coefficient of variation inflow fit factors was much lower, ranging fr om 1.7% for the top probe to 2.2% for the center and bottom probes.