74 



THE NAVY OCEAN ENGINEERING PROGRAM 



Diver with Mark VI semiclosed- 

 circuit mixed-gas scuba. The Mark 

 VI is a recirculating scuba using 

 mixtures of nitrogen-oxygen or 

 helium-oxygen. Exhaled gas is 

 forced through a CO2 removal 

 canister and reused. Excess gas is 

 bled off through a relief valve. 

 This apparatus permits the diver 

 more time at depth than the scuba 

 equipment commonly used by 

 civilian skin divers. 



Back view of the Mark VI semiclosed- 

 circuit mixed-gas scuba. Utihzing special 

 breathing fixtures, this apparatus permits 

 the diver more time at greater depths 

 than the standard scuba rig. 



