A breathing apparatus has first bellows and second bellows, the first bellows being so designed as to expand by a part of air exhaled by the diver or wearer of the breathing apparatus being supplied thereto through a mouth piece and the second bellows being so designed as to contract as the pressure of a surrounding atmosphere around the breathing apparatus, i.e., the atmospheric pressure under water. When the sum of an expanded amount of the first bellows and a contracted amount of the second means reaches a value which is equal to or larger than a predetermined value, an exhalation discharge valve disposed on a mouth piece is so opened as to discharge the exhaled air into a surrounding atmosphere around the breathing apparatus. This arrangement for the breathing apparatus enables the number of times of re-utilizing the exhaled air as air for inhalation to increase as the pressure of the surrounding atmosphere increases.

Patent information supplied by Mr. Ken Culotta, thank you very much for your contribution!