Momsen lung

The Momsen lung was a primitive underwater rebreather used before and during World War II by American submariners as emergency escape gear.

[3] The device recycled the breathing gas by using a counterlung containing soda lime to remove the carbon dioxide.

[5] Thirteen men (of thirty survivors) left the forward escape trunk:[6] five were picked up by the Japanese; three more reached the surface "but were unable to hang on or breathe and floated off and drowned"; the fate of the other five is unknown.

They adopted the practice of "blow and go" in which the sailor would exhale before ascent to avoid air over-expanding the lungs, which could cause them to rupture.

Walter F. Schlech, Jr. and others examined submerged escape without breathing devices and discovered that ascent was possible from as deep as 300 ft (91 m).