Patent ID: 6712071
Filing Date: 2004-03-30
Classification: A62B,B63C

Abstract:
Self-contained breathing apparatus of the type having a container (16) for receiving exhaled gas having an oxygen content, means (19) for removing carbon dioxide from the exhaled gas, oxygen sensor means (51, 52, 53) for detecting the oxygen content of the exhaled gas, the sensor means providing output signals indicative of the oxygen content, and means (20, 22) for injecting oxygen into the exhaled gas to reinstate the oxygen content so as to lie within a desired range for re-breathing, characterised in that the signals from the oxygen sensor means (51, 52, 53) are delivered to two independent signal processing circuits (59, 60) which are interconnected in a primary and secondary relationship with the primary signal processing circuit acting in use to control a solenoid valve (22) for injection of oxygen into the exhaled gas and the secondary signal processing circuit acting in use to display (61, 62) information concerning the sensor output signals to provide confirmation of the satisfactory operation of the primary signal processing circuit wherein either of said signal processing circuits may function as the primary signal processing circuit while the other of the signal processing circuits may function as the secondary signal processing circuit.