Determination of Inspiratory Pressures and Flow Rates for Work Rate-Dependent Quantitative Respirator Fit Testing

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Abstract
Quantitative respirator fit testing is used to select respirators for individual workers and to gain insight into potential contaminant leakage. Current fit test exercises are designed to primarily challenge the respirator face-piece-to-face seal. Inspiratory pressure across any break in the seal is also an important determinant of the amount of leakage through the break. Fit tests conducted at resting respiratory patterns may not be representative of leakage that occurs at respiratory patterns employed in the workplace. By design, the controlled negative pressure fit test method can control the driving force for leakage into a respirator by selecting a challenge pressure that represents actual use inspiratory pressures. In this study, mean inspiratory pressures and flow rates were determined for males and females working at external work rates of 0, 180, 360, and 540 kg · m/min. Effects of mask type and breathing resistance were determined using both half-mask and full-face respirators equipped with cartridges of relative low, medium, and high breathing resistance. Inspiratory pressure was found to be strongly dependent on work rate and cartridge resistance. Mask type and gender also had significant effects on mean inspiratory pressure. Inspiratory flow rate was significantly affected by work rate and mask type. Data from the study can be used to conduct work rate-dependent fit testing with the controlled negative pressure method. Crutchfield, C.D.; Pham, T.K.; Van Ert, M.D.; Determination of Inspiratory Pressures and Flow Rates for Work Rate-Dependent Quantitative Respirator Fit Testing. Appl. Occup. Environ. Hyg. 8(2):103-107; 1993.