Oxygen use:
is NOT depth dependant.O2 is used as it is metabolized by the body in direct relationship to workload ONLYMost rebreathers utilize a 20 cf (600 litre) bottle or greater capacity.The average diver metabolizes about 1 litre per minute. If working moderately the diver may metabolize 1.5 litres. If working hard, perhaps 2 litres.600 litres / 1 lpm = 600 minutes / 60 minutes = 10 hours600 litres / 1.5 lpm = 400 minutes / 60 minutes = 6.6 hours600 litres / 2 lpm = 300 minutes / 60 = 5 hoursThese calculations are NOT depth dependant!!consider the cost of Oxygen: approximately .30 per cfUp to 10 hours of diving nitrox costing $6.00 in O2 fill.Diluent use:
One breath is contained in the counterlung. If you dive to 99 fw you should use the equivalent of 4 breaths of air during the dive + buoyancy inflationusing helium; since no gas is expired to the environment the only gas you use is inflation of the counter lungs on descent.Diving to 300 ft would require as little as the equivalent of 10 breaths, FOR THE ENTIRE DIVE!