Patent ID: 7762252

Claim:
A breathing system comprising: a source of pressurized breathing gas; a regulator assembly comprising an inlet for connection to the source of pressurized breathing gas, an outlet to provide breathing gas to a user and a valve assembly for controlling flow of breathing gas between the inlet and the outlet based at least in part on the respiration of the user; an actuator via which flow of pressurized breathing gas from the source of pressurized breathing gas to the inlet of the regulator assembly is started when the actuator is placed in a first state and is stopped when the actuator is placed in a second state; a facepiece comprising a first port adapted to be placed in fluid connection with the outlet of the regulator assembly to introduce pressurized breathing gas into the facepiece, a second port adapted to be connected to an air purifying system; and an exhaust valve through which the user's exhausted breath can exit the facepiece; and a pressure adjustment mechanism in operative connection with the exhaust valve and operable to adjust the internal facepiece pressure required to open the exhaust valve, the pressure adjustment mechanism including a communication link in communicative connection with the actuator such that the exhaust pressure adjustment mechanism sets the internal facepiece pressure required to open the exhaust valve independently of respiration of the user to a first pressure when the actuator is in the first state and the pressure adjustment mechanism sets the internal facepiece pressure required to open the exhaust valve to a second pressure when the actuator is in the second state, the first pressure being higher than the second pressure; wherein the communication link of the pressure adjustment mechanism comprises a pneumatic fluid path providing fluid connection of pressurized breathing gas prior to reduction of pressure of the pressurized breathing gas in the regulator assembly to the pressure adjustment mechanism when the actuator is in the first state and preventing fluid connection of pressurized breathing gas to the pressure adjustment mechanism when the actuator is in the second state.