Belize Diving Death; Always Test Your Air

While divers know to analyze their nitrox before a dive, they may not think it important to analyze compressed air. But, with operations producing all sorts of mixes these days, one should analyze both nitrox and air.

This was borne out by an incident in Belize on June 14 when two nitrox divers became ill during a benign 60-foot dive. Initial reports tell that the Belizean divemaster leading the group was recovered by a woman in the group breathing straight air, who successfully administered CPR at the surface. The other diver, a US citizen, appears to have made an uncontrolled ascent leading to embolism and death after he became unwell at depth. He sank back down from the surface to the seabed.

The contents of their tanks are suspected of either being contaminated with CO or having a too-rich oxygen mix, leading to toxicity at depth. The dive operator was Ambergris Divers, which has not responded to our request for more information.

It's unlikely CO poisoning was the culprit since that would have been due to a faulty compressor installation and affected more tanks. All the other divers appeared to have no problems.

It's more likely that the nitrox mix is suspect. This can happen especially if the nitrox is made by partial pressure blending (when neat O2 is added to a tank and then topped up with air) rather than de-nitrogenizing air through a membrane system. CO analyzers tend to be expensive and complex to use - but anyone can buy a personal nitrox analyzer. They can cost around a couple of hundred dollars (Vandgraph, Divesoft, etc). Always check to know what you're breathing - even if you think you're getting straight air.

- John Bantin