RESPIRATOR PERFORMANCE FOR STEL EXPOSURES IN THERMAL ENVIRONMENTS

Maintenance workers are often required to wear respirators for protection from airborne contaminants in the workplace. Adverse working conditions such as low air velocity, high temperature and humidity, the wearing of impermeable protective clothing and the metabolic demands of the work exert significant thermal stress on the workers especially during the performance of certain maintenance tasks and especially in thermal environments. The wearing of respirators has been determined to contribute to heat stress during thermal conditions; however, the effects of a thermal environment on respirator performance, particularly of the face-to-respirator seal have received little attention. An irritant smoke qualitative field test procedure was developed and used to evaluate the performance of rubber and silicone facepiece models of a half-mask air-purifying respirator under thermal and non-thermal working conditions for 37 maintenance workers at a coal-fired, electrical power generation plant.;Half-mask respirators of the type studied were found to provide inadequate protection for STEL exposures in thermal environments and may be inappropriate for use for a large percentage of the working population. The irritant smoke qualitative field test procedure was shown to be effective for evaluating short-term performance of negative pressure, half-mask respirators, providing there are no interfering air currents, where HEPA or HEPA combination cartridges will provide adequate respiratory protection.;Prior to participating in field testing, subjects were screened using an irritant smoke qualitative fit test. During initial fit testing, 30 per cent of the subjects failed to fit, and additional failures in subsequent tests resulted in an overall failure rate of 42 per cent. The subjects experienced respirator failures in both thermal and non-thermal environments even after the "poor fits" had been eliminated the by use of a fit test. Over 90 per cent of the failures in the thermal environment and all of the failures in the non-thermal environment occurred within the first 9 minutes of the 15-minute test period. The effectiveness of respirators of both facepiece materials was decreased significantly (p < .05) during thermal working conditions.