Gas work with sensing and alarm means

Claim 1

A gas mask having air aspiration means, said gas mask comprising: battery means for providing electrical power to various components of the gas mask; filter means, said filter means having an upsteam side in communication with the ambient air and a downstream side in communication with a user of the gas mask; electrically operated means for producing a flow of ambient air into and through said filter means for supply to the user of the gas mask; electric sensing means disposed on said downstream side of said filter means for sensing at least one gas in the flow of ambient air that affects the breathing of the user of the gas mask; said electric sensing means comprising means for providing a variable electrical signal corresponding to the amount of said at least one gas present in the ambient air downstream of said filter means; processing means for processing said variable electrical signal to produce a processed signal corresponding to said amount of said at least one gas; alarm means responsive to said processed signal for providing an alarm when said amount of said at least one gas is outside of a range; said alarm means being for indicating an inadequacy of said filter means for protection of the user of the gas mask; wherein said at least one gas consists essentially of oxygen and wherein said electric sensing means comprises oxygen decomposing means.