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Development of a dichotomous-flow quantitative fit test for half-mask and full-facepiece respirators.

Krishnan U; Willeke K; Juozaitis A; Lehtimaki M; Szewczyk K
Am Ind Hyg Assoc J 1994 Mar; 55(3):223-229
A new technique for quantitating the fit of elastomeric half mask and full facepiece air purifying respirators (the dichotomous flow respirator fit test) was developed. The test involved the subject donning test respirator while its cartridges were mounted on a reference respirator. The open side of the reference respirator was sealed and the respirator was connected to a rigid fixture. Air was drawn through the cartridges at fixed flow rates chosen to be representative of inhalation flow rates during light, medium, or heavy work activity. Two modified cartridges were attached to the test mask and separated cartridge flow from the leak flow. A feedback system consisting of a pressure controller and a control valve was used to set the pressure drop in the test mask equal to the pressure drop in the reference mask. Faceseal leak flows in the test mask were measured while the wearer held his breath for a short period by sampling probes placed inside the mask. The ratio of the total flow (cartridge flow + leak flow) to the leak flow was taken to be a measure of respirator fit and was defined as the flow fit factor. The technique was evaluated using half masks or full face respirator masks sealed on mannequins that were exposed to a room aerosol and with leaks introduced at the top, center and bottom of the masks. The results were compared with results obtained using the standard aerosol penetration test. Representative data indicated that for a 1.07 millimeter diameter faceseal leak introduced in a half mask, flow fit factors determined by the dichotomous flow respiratory fit test were the same, 520, at each location. Fit factors determined by the standard aerosol penetration test varied from 640 to 1,000. The overall relative coefficients of variation (RCVs) for replicate determinations of fit factors determined by the dichotomous flow respirator fit test varied from only 1.7 to 2.2%. RCVs for fit factors obtained by the standard aerosol penetration test ranged from 5.4% at the center probe to 19% at the bottom probe. The authors conclude that the dichotomous flow respirator fit test has distinct advantages over the conventional aerosol penetration test: noninvasiveness and portability.
NIOSH-Publication; NIOSH-Grant; Respirators; Respiratory-protective-equipment; Laboratory-testing; Industrial-hygiene; Leak-detectors; Air-flow
Environmental Health University of Cincinnati Dept of Environmental Health Cincinnati, Ohio 45267
Publication Date
Document Type
Journal Article
Funding Amount
Funding Type
Fiscal Year
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Priority Area
Respirator Research; Respirators
Source Name
American Industrial Hygiene Association Journal
Performing Organization
University of Cincinnati, Cincinnati, Ohio
Page last reviewed: September 25, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division