Oxygen masks are well known in the art as a tool for fighting fires in an enclosed structure. A portable oxygen mask that can provide a steady and controlled stream of oxygen while maintaining a weight that allows for freedom of movement is a necessity when fighting fire. This need is never more prevalent than in the confined and pressurized environment of an aircraft. An aircraft fire presents many additional dangers due to its pressurized compartments and the presence of oxygen in large quantities. Therefore, there is a need in the art for a reliable and compact oxygen mask that is light weight and well suited for all closed environments, and particularly those of an aircraft.
One difficulty with present masks, or protective breathing equipment (“PBE”) as they are known, is that it is difficult or sometimes impossible to determine when the oxygen or carbon dioxide levers are approaching dangerous levels. Sometimes in the excitement of fighting a fire, the adrenaline will cause the user to extend the fire fighting activities until becoming light-headed or passing out, causing a significant danger to the user. Since it cannot be determined whether the unit is still operating correctly, the user in many cases must remove the mask and either replace it or recharge it before being able to return to fighting the fire. If there were a reliable way for the user to monitor the oxygen and carbon dioxide, this would also allow the PBE user to wear the unit longer.
In view of this difficulty, the new version of the FCC crewmember PBE regulation (TSO-C11a) requires “failure of the unit to operate or to cease operation must be more apparent to the user. This must be accomplished with aural and/or visual warning that also must activate at gas supply exhaustion.” The present invention seeks to address this issue, thereby meeting this portion of the requirements of TSO-C116a.
U.S. Pat. No. 5,613,488 to Schwichtenberg et al. discloses a chemical oxygen generator breathing device that seeks to achieve a level of availability of oxygen and aims to optimize the consumption of oxygen. However, the Schwichtenberg device is complex, expensive, and only deals with oxygen.