Abstract: The invention relates to a breathing apparatus for an aircraft crew member, said apparatus comprising at least one breathing mask (620) provided with a demand regulator (810), said demand regulator being linked through a feedline to a central source of oxygen enriched air (600), so that oxygen enriched air is supplied to said breathing mask, and pressure regulating means (601,602,603, 604) provided on said feedline between said central source and said demand regulator and adapted, to level the pressure fluctuations of said oxygen enriched air supplied to said breathing mask.

Abstract: A demand valve for use in breathing apparatus, and comprising a housing 1 in which is mounted a diaphragm 2 such as to divide the interior of the housing into two separate chambers 3,4. Chamber 4 is vented to atmosphere through a hole 14; chamber 3 is connected via a pipe 13 to a gas outlet whereby breathing gas may be supplied to a face piece or mask for a user. Breathing air is supplied from a main gas supply channel 8 via a main valve 9,10 to a gas supply channel 6. A gas inlet channel 5 connects the supply channel 6 to the chamber 3 under the control of a needle valve 11 which closes an orifice 7. The head 11B of the needle valve is urged by a spring (not shown) into contact with the diaphragm 2 and thus the movement of the diaphragm controls the opening and closing of the needle valve. The diaphragm 2 is pivoted about spaced pivot members 15, and leaf springs 16 are used to maintain the diaphragm in contact with the pivot members 15.

Abstract: In a combined gas flow control regulator and pressure relief valve, the pressure relief valve includes a pressure relief member comprising a flange and a sleeve which is sealingly engaged with the piston rod of the gas flow control regulator and is slidable relative to the piston rod. A spring urges the flange of the pressure relief member into contact with the piston head of the gas flow control regulator thereby closing a gas relief aperture in the piston head capable of connecting a first chamber, which is one chamber of the gas flow control regulator to a second chamber which is a gas relief chamber from which gas can escape to atmosphere.