Patent ID: 6892730

Claim:
A flexible oro-nasal mask for mounting in a rigid shell attached to a helmet of aircrew at a fixed distance therefrom, the flexible oro-nasal mask comprising an inspiratory and expiratory valve and a periphery of the mask being adapted to make a seal with a wearer's face, the oro-nasal mask comprising: an extendable means operable to press the periphery of the mask automatically towards the wearer's face to improve the seal therewith when gas at a pressure above that for normal breathing is supplied to the mask and the extendable means reconfigured as a result thereof, the extendable means being configured so that when the gas is supplied to an interior of the mask, a portion thereof in a bottom region of the mask extends more than a portion in an upper region of the mask so that the bottom of the mask is moved away from the wearer's face by a greater amount in a chin region of the wearer's face than in the nose region of the wearer's face, whereby the mask is capable of pivoting upwardly automatically to compensate for effects of G forces.