AN INVESTIGATION INTO THE PERFORMANCE OF POSITIVE PRESSURE POWERED DUST HOODS AND BLOUSES AT LOW FLOW RATES *

Abstract

Tests were performed to determine the inward leakage into high-efficiency positive pressure powered dust respirators fitted with a hood or blouse. The breathing rate was held constant by means of a breathing simulator and the flow of filtered air varied. The concentration of aerosol within the device remained below 0.1% of the ambient concentration even when the peak inspiratory flow exceeded the flow into the device. Because of the greater volume of air trapped within the blouse. this device afforded better protection at the lowest flows, but the reinhaled carbon dioxide was also greater. An investigation into the performance of these devices following a simulated power unit failure revealed a rapid increase in the concentration of carbon dioxide and a similar increase in the inward leakage. They are thus not suitable (unlike full-facepiece powered respirators) for use in conditions where adequate protection must be maintained in the event of power failure.