A comparison of controlled negative pressure and aerosol quantitative respirator fit test systems by using fixed leaks.
Crutchfield CD; Murphy RW; Ert MD
Am Ind Hyg Assoc J 1991 Jun; 52(6):249-251
An automated negative pressure system for quantitative respirator fit testing was evaluated. The system consisted of a pressure transducer, a mass flow controller, pulse dampener and pressure relief valve connected to a vacuum pump, digital voltmeter, and computerized data acquisition system. It was tested with a 1 liter canister configured to simulate a sealed respirator using a reference pressure of -1.50 centimeters of water. A series of fixed leaks were introduced into the system by four hypodermic needles having inside diameters of 0.025 to 0.084 centimeters (cm) and lengths 2.5 or 4.5cm. This produced leak rates of 3 to 108 milliliters (ml) per minute. Predicted equivalent fit factors were computed by dividing leak rates measured in the canister into a previously derived mean inspiratory flow rate of 431ml per second. The results were compared with those obtained by a standard computerized aerosol fit test system that used the same hypodermic needles inserted through a septum mounted on a Y-fitting leading into a cartridge respirator and corn-oil as the test aerosol. Fit factors obtained by the negative pressure system and aerosol system ranged from 274 to 9901 and 348 to 15165, respectively. Regression analysis revealed that the negative pressure and aerosol fit factors were highly correlated, correlation coefficient 0.997. The fit factors were also correlated with the cross sectional areas of the needles, correlated coefficient 0.995. The authors conclude that equivalent fit factors obtained with the automated negative pressure test system are highly correlated with those obtained by an automated aerosol fit test system.
NIOSH-Publication; NIOSH-Grant; Respirators; Laboratory-techniques; Respiratory-protective-equipment; Pressure-testing; Air-flow; Laboratory-testing; Simulation-methods; Statistical-analysis
Pharmacology and Toxicology University of Arizona 1435 N. Fremont Ave Tucson, AZ 85721
Respirator Research; Respirators
American Industrial Hygiene Association Journal
University of Arizona, Tucson, Arizona