Importance

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Abstract

A positive pressure filter respirator includes a full face mask comprising an outer mask 1 and an inner orinasal mask 2. A filter canister 5 is screw mounted to an air inlet 4, and a centrifugal fan 6, which is driven by a battery operated motor 7, is so arranged as to draw air through the filter canister 5 into the outer mask 1. The filter life and the battery life are extended by the use of a pressure responsive means which responds to the difference in pressure between the pressure in the interior of the orinasal mask 2 and the pressure in the space 20 within the outer mask 1 and outside the orinasal mask 2. The pressure responsive means reacts immediately to the commencement of either exhalation or inhalation to disable the fan 6 or on commencement of exhalation and to accelerate the fan 6 on commencement of inhalation. The pressure responsive means comprises a diaphragm 9 and an infra-red proximity detector 10 mounted close to the diaphragm 9, and as described, the pressure responsive means acts to switch off the fan 6 at the commencement of exhalation and to switch the fan 6 on at commencement of inhalation.

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First Claim