Emergency Breathing from Your BC

You’re 100 feet down with two buddies. Both come to you out of air. What do you do?

If you’re as experienced and alert as one diver we know of, you could pass your primary second stage to one buddy, give your octopus to the second, then begin a slow ascent valving fresh air into your buoyancy compensator and breathing through your BC’s oral inflator mouthpiece. It’s a little tricky and takes some practice, but it works. Yet none of the commercial training agencies teaches BC breathing at any level. In fact, since we first reported on this technique several years back, the industry seems to have closed ranks against it, even though it’s been successfully tested in a variety of predicaments.

We’re hardly advocating breathing BC air as a standard practice — only as a last resort. Even if you suck your tank dry, you can get some air through your regulator as you ascend and the air in your tank expands. But once your tank is bone dry, you’ll still have residual air in your BC (or at least in your inflator hose). If you added air with your power inflator, it will be pure and contain 21% oxygen. If you orally inflated your BC, it will still contain 16% oxygen.

Bear in mind that air in your BC will also expand as you rise. If you put your BC mouthpiece in your mouth and keep trying to inhale and exhale while you rise, you should be able to do without air for at least 20 seconds. By then, air volume will have increased enough to provide a breath. Studies conducted by the late Al Pierce of the YMCA concluded that you can exhale back into your BC and keep rebreathing the same air 13 times or more without becoming overly hungry for fresh air. (After all, exhaled air is good enough for artificial respiration.) With this technique, instead of free-ascending with no air, you’ll have some air as you rise, which will allow you to make a slower and safer ascent.

Even so, agencies refuse to teach this technique at any level. The key objection voiced by SSI, PADI, and even DAN seems to be the possibility of respiratory infection from bacteria inside the BC. However, BCs used for training can be disinfected with solutions readily available in dive shops. Or you can use benzalkonium chloride, which is available at drug stores under the brand name Zephiran chloride. Apparently the Coast Guard uses Listerine. Besides, why should you be concerned about a lung infection in an emergency? There are a helluva lot more cures for respiratory infections than there are for drowning.

The second biggest objection made by training agencies is that divers will need to master new skills and perhaps to overlearn some old ones. For instance, you must be able to clear the ounce or so of water from your inflator hose mouthpiece without choking. Other skills required vary depending on whether your first stage is still supplying air. Additional objections include difficulties with buoyancy control, such as ascending too fast or the possibility of arriving on the surface with no lift in the BC.

Frank Toal of NAUI summed up the attitude of the certifying agencies and manufacturers we contacted by stating that BC breathing “...could be used as a last-ditch effort versus drowning, but, because it is at best a very difficult technique, it is not taught in any course as required training.” He also brought up the decadesold bugaboo about the potential for carbon dioxide poisoning if a CO2 cartridge had ever been fired to inflate the BC. Of course, if you’re still diving with a BC that old-fashioned, you’re probably too stubborn to learn new skills anyway.

The consensus seems to be that keeping things simple reduces the chance of panic. Retired UCLA professor Glenn Egstrom cites a phenomenon called “peripheral narrowing,” which is the tendency to lose track of one’s options under stress, thereby subverting the reflexive nature of trained responses. While that may be a valid consideration, does it make sense for those charged with the safety of others (e.g., Rescue, Divemaster, or Instructor levels) to not even be exposed to this proven technique for handling out-of-air situations or equipment malfunctions?

Dave Walls of PADI spelled out his agency’s recommended options for low/out of air situations, in order of priority:

1. Make a normal ascent, if your tank isn’t completely empty;
2. Ascend using an alternate air source (redundant supply or buddy’s octopus);
3. Execute a controlled emergency swimming ascent;
4. Buddy-breathe with a single regulator supplied by another diver;
5. Make a buoyant emergency ascent.

However, isn’t a controlled emergency ascent or a buoyant emergency ascent safer if you have a few breaths of air from your BC? Knowing you’ve got at least one more ace up your sleeve might help keep you cool as you weigh your options. Hopefully, you’ll get things under control before you ever need to use your BC as an alternate air source. But it’s there if you need it.

— D. L.