| 摘要 |
The present invention is directed to a closed circuit underwater breathing apparatus having a mouthpiece and an outward and return connection leading from the mouthpiece to an inflatable breathing bag and back respectively to form a breathing circuit. A carbon dioxide absorbent is arranged in the breathing circuit. In use, exhaled gases flow from the mouthpiece through the outward connection to expand the breathing bag and then, on inhalation, they return from the breathing bag through the return connection to the mouthpiece. The apparatus also includes a demand valve controlling a connection between the mouthpiece and an inlet for an attachment to a supply of breathable gas. The demand valve so operates automatically to open the connection between the inlet and the mouthpiece when inhalation demand through the mouthpiece is not completely satisfied by the gases from the breathing bag so that the inlet connected to a supply of breathable gas is opened and the operation of the demand valve allows sufficient gas from the supply of breathable gas to enter the mouthpiece to complete the satisfaction of inhalation demand.
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