A Catastrophic Regulator Failure

My first article for the British magazine Diver in the mid-'80s came as the result of an upstream regulator failing on me during a dive on a wreck near Pula Putri in Indonesia. Upstream regulators cut off the air supply if they fail, and thankfully they are no longer available for sale in stores. When a modern downstream regulator fails, it free-flows.

Peter Buzzacott, the former director of monitoring and injury prevention for Divers Alert Network, wrote an article in Alert Diver about such a catastrophic regulator failure. He cites the case of a 36-year-old woman diving in the Solomon Islands whose new regulator failed when she was nowhere near another diver who could offer her an alternate air supply. She appeared to have plenty of air in her tank, but her regulator had jammed shut. She made a free ascent from 53 feet deep, was put on therapeutic oxygen as a precaution, and luckily suffered no ill effects, even though she had been down as deep as 91 feet.

In my case, I had to make a free ascent from 66 feet on a no-stop dive. No big deal, as it happened, but not something I'd recommend anyone to practice. It did give me insight into the sudden loss of an air supply, and probably made me a better diver for the experience. (The downside was that article, when published in Diver back in 1985, gave me the taste for diving journalism, a profession that barely covers the bills, let alone the price of an Indonesian dive trip.)

Every diver should be aware of how to breathe from a modern free-flowing regulator. Hopefully, you were taught what to do in your basic scuba course: You hold the mouthpiece at an angle in your partially open mouth so that excess air escapes freely into the water while you make a safe ascent.

The woman Buzzacott wrote about had no option to do that. However, the Auto Closure Device (ACD), introduced on some regulators a few years ago, can produce the same effect as an upstream regulator if it fails -- it can cut off the air supply. In fact, there was a recall of such regulators made by Aqua Lung (we wrote that up in our November 2017 issue), and the Solomon Island diver had a regulator with an ACD that failed when closed and blocked her air supply.

The ACD once seemed a good idea because the intention was to stop water from getting into regulator first-stages if they were dumped into the freshwater rinse tank without the blanking cap securely in place. Not so good if it fails and prevents air passing from the tank.

While you have air in your tank, a modern regulator will always supply it, even if it gushes uncontrollably. If it does fail, it will usually happen at the beginning of a dive, when your tank has the greatest gas pressure in it.

If you solo dive, you should carry an adequate second tank -- not a Spare Air -- to get you safely to the surface from the depth to which you habitually dive.

If you do need to make a free ascent because your tank went empty, you know better than to hold your breath -- to avoid a lung over-expansion injury, with probable fatal consequences. The best trick for keeping your airway open to allow that expanding compressed gas to escape is by shouting "Arrgghhh!" as you ascend.

So, if you bought an ACD version of a regulator, best avoid using it. Instead, develop a strong habit of fitting the blanking cap to the first-stage before dunking it in the rinse tank.

-- John Bantin