Protective breathing apparatus having breathing air circulation

Claim 1

A protective breathing apparatus for a user inhaling a volume of gas and exhaling a volume of gas, comprising: a user connection line adapted for connection to the user; an inhale line connected to said connection line; a first check valve in said inhale line for permitting passage of gas only toward said connection line through said inhale line; an exhale line connected to said connection; a second check valve in said exhale line for permitting passage of gas only from said connection line through said exhale line; lung controlled oxygen supply means connected to said inhale line for supplying oxygen to said inhale line upon a falling of pressure in said inhale line due to the unsatisfied demand of the user; a storage space unit connected to said inhale line and to said exhale line, said storage space unit including a partition wall dividing said storage space unit into a first storage space portion, which includes the connection to said exhale line and a breathing bag space portion, which includes the connection to said inhale line; said first storage space portion comprising a wall opposite from said partition wall and a first expandable bellows connected between said wall and said partition wall, the volume defined by said first storage space portion being expandable up to a maximum volume comprising at least a plurality of exhalation volumes of the user, said breathing bag space portion comprising a breathing bag sealingly connected to the surface of said partition wall opposite said first storage space portion and a transfer means connected through said partition wall for opening communication between said first storage space portion and said breathing bag space portion only after said maximum volume of said first storage space portion has been reached.