-1.4 Gas Distribution

1.4 Gas Distribution

Catastrophic loss of high-pressure gases is a very minimal risk; however, failure of low-pressure gas delivery devices should be considered. These considerations are not different from mitigating the very same concerns in open-circuit diving. On the diluent side, the alphabet soup of devices – ADV, MAV, and BOV – are typically supplied from a single diluent supply. Each device should provide a means to be isolated in the unlikely event of device failure or failure of its supply hose. Ideally, a separate and redundant diluent supply should be capable of being introduced by the diver or by a member of the diving team. This is easily achieved with some strategy placed on plumbing components and partially mitigated by placing consideration on use of hoses that are overrated for the working pressure.

Likewise, on the oxygen side, a solenoid, MAV, and orifice or needle valve, should be capable of being isolated and an external oxygen supply should be introduced.

Simply put, in principle, there must be a redundant means for introducing oxygen and diluent gases into the breathing loop, particularly as we consider that the diver is heavily dependent on staying on the breathing loop through long and exhaustive decompression profiles.

In both oxygen and diluent systems, we must not become fearful and further paralyzed by a component failure. In all cases, failure risk of these components is no greater than a free flowing open-circuit regulator, or a drysuit valve sticking open. It happens, but it’s rare and routine maintenance of these component parts should be part of the service regimen for all the diver’s equipment. Again, when considering maximizing the rebreather‘s potential in extended range diving, it is reasonably easy to be prepared for these minimal but foreseeable risks, and risk mitigation is what we strive to be all about in carrying the art forward.

Here, very basic subassemblies for both diluent and oxygen will be broken down and discussed. Numerous variations of component parts are commercially available, and numerous others have been custom configured by end-users. In the end, it is up to the end user to make an educated decision on design of the best gas distribution system for his/her diving needs. The concepts presented below are basic guidelines and considerations of feature sets for design and integration of this hardware into a rebreather and the solutions selected for my own rebreather technology development and assemblages.