The Secretary of State for Defence in Her Majesty's Government of the

Ian A Himmens

A diver's mask for use in contaminated water includes a shroud (12) which manifolds the demand regulator exhale port (7) with a second exhale port (9) from the diver's oral/nasal mask (2) to form a gas filled cavity (11). The shroud (12) has an outlet port (13) to the surrounding water (15). When the diver breathes out exhaled gas enters the cavity (11) and the pressure causes the non-return valve (14) of the outlet port (13) to open, allowing gas to escape from the cavity (11) into the surrounding water (15). When the diver stops exhaling, the pressure of the water (15) causes the non-re turn valve (14) to close, leaving a residue of exhaled gas in the cavity (11). When the diver inhales again, the outlet port non-return valve (14) prevents water being drawn into the cavity (11) and non-return valves (8,10) of the exhale ports (7,9) prevent the exhaled gas from being drawn back into the inhaled gas.

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Portsmouth, United Kingdom

Ian A Himmens