The Mark 15 Closed Circuit Mixed Gas Rebreather was built for the US Navy by a couple of companies, most notably Rexnord, Inc. and BioMarine Industries.
Essentially, the Mark 15 was used for EOD work in the Navy – that is, Explosive Ordinance Disposal. They wanted a device that was quiet, and emitted no bubbles. Later, they required a device that was non-magnetic – so they developed the Mark 16 and later, to upgrade their existing Mark 15’s, the Mark 15.5.
The Mark 15 is a closed-circuit, mixed gas rebreather which can use compressed air, Trimix or Heliox as a diluent, depending on the depth of the dive, and the preferences of the diver.
The Mark 15 controls the partial pressure of oxygen supplied to the diver to +/- 10% of the set point. This set point is selected during the calibration procedure and may vary from 0.5 to 1.3 atmospheres.
For most diving applications, an Oxygen partial pressure of approximately 1.2/1.3 is recommended.
Assuming appropriate decompression and support equipment is available, the unit can be used for up to 6 hours of diving, independent of depth. The record depth for diving a unit of this kind was set by a diver working out of a saturation lock-out bell at 1,800 feet.
For any diver wishing to have a unit that has been tried and tested and never been found wanting then the Mark !5 series will provide you with all you want.