Closed Circuit Rebreathers are for Solo Divers

Closed-circuit rebreathers are becoming ever more popular with divers. Martin Parker of APD, manufacturer of a popular CCR, estimates there are currently around 25,000 users of the APD Inspiration, and there are several other rebreather manufacturers.

On July 6, two Polish divers who live in the UK made a technical dive in strong currents to Malta's 165-foot-deep wreck of Le Polynesien. Using closed-circuit breathers, they made a fast ascent, missed mandatory decompression stops, and died as a result. It's believed that one got into difficulty, and the other tried to help him.

So why the fatal outcome? No one knows what difficulty the first diver encountered, but if it was entanglement, a CCR gives you plenty of time to sort things out. It's more likely it was a problem with the rebreather itself.

There are two or three likely scenarios. The first is that it was giving him the wrong gas mix. This would only be likely if the problem was encountered early, in which case the onboard computer would have made audible and visual warnings long before it had a physiological effect and he could have returned to the surface. Similarly, if he'd experienced a loop flood, that would have happened long before he got to 165 feet deep. More likely, the first diver was suffering carbon dioxide poisoning.

CO2, the waste product of metabolism, is filtered out of the breathing loop by a canister of Sofnolime, but the canister must be filled correctly. If not, CO2 can pass back into the breathing loop and be rebreathed. It's a very dangerous gas to breathe at depth and can lead to out-of-control breathing, panic, and even a heart attack.

The second diver tried to help him. Nowadays, CCR divers also carry an open-circuit bail-out rig (conventional scuba) for such emergencies, but it's my real-life experience that the confusion and panic brought about by CO2 poisoning makes this less than viable. Also, were they carrying enough gas in their bail-out rigs to get safely to the surface from 165 feet, including mandated deco stops?

It is virtually impossible to buddy breathe from another diver's CCR. So, the would-be rescuer has little in the way of options. They both ended up hurtling to the surface and died because of it. It was a tragedy, but the second diver was, in fact, a hero because he tried to intervene. What else could he do?

I've had extensive experience with CCRs, but I stopped using a rebreather when I reached my sixties because I realized I was no longer sharp enough to cope with any of the inevitable problems I had successfully managed in the past.

It is very difficult to rescue a CCR diver who is in trouble with his breathing gas while at depth. It's a double tragedy that the rescuer also lost his life in this incident.

If you use a CCR, you have terrific advantages regarding gas consumption and decompression requirements, but you are on your own. If you don't prepare your CCR correctly, it might kill you.

In the past, Undercurrent has recommended what all divers, whether CCR divers or not, should know about closedcircuit rebreathers. You can read my story by clicking here. (https://tinyurl.com/v3jv9wux)

- John Bantin, Senior Editor