Respirators

Apparatus for supplying respirable gas to an aircrew respirator of the type having a hood with a cowl and visor adapted to envelop at least the face of a user and a mask for delivering respirable gas to the user, means for maintaining a gas pressure within the hood but outside the mask greater than that outside the hood and for preventing misting of at least a portion of the visor, said apparatus comprising:

• a control unit including an air supply manifold and an oxygen supply manifold and mountable in the region of the aircrewman's chest,
• a flexible respirable air supply duct connected into said air supply manifold and adapted for connection to a filter/blower unit,
• a flexible mask supply duct connected to the said supply manifold and adapted for connection to the respirator mask,
• a flexible hood supply duct connected to said air supply manifold and adapted for connection to the respirator hood cavity external to the mask,
• a non-return valve lightly biassed closed in said hood supply duct approximate said control unit and permitting therein in use only flow of gas from said air supply manifold to the hood,
• a flexible oxygen supply duct connected to said oxygen supply manifold,
• a flexible mask oxygen supply duct contained within said mask supply duct, connected to said oxygen supply manifold, and terminating with an exit just upstream of the connection for said mask supply duct to the mask,
• a restriction in said mask oxygen supply duct for controlling the flow of oxygen therethrough,
• a flexible emergency hood gas supply duct contained within said hood supply duct connected to said oxygen supply manifold and having a restrictor therewithin and an exit in said hood supply duct downstream of said non-return valve,
• a cock on said control unit for determining whether oxygen shall flow in said emergency hood gas supply duct, and
• an anti-drowning facility whereby said mask supply duct can be manually disconnected from the respirator mask at the connection thereto,
• the total capacity of said mask supply duct and said air supply manifold being such that sufficient oxygen can be stored therein between inspirations to ensure on inspiration a predetermined minimum within a range of partial pressures of oxygen in the respirable gas and surplus oxygen can enter said hood supply duct during prolonged non-inspiration.