“Always analyse your gas” – Statement from the NACD

Following a recent fatality at Ginnie Springs, the National Association for Cave Diving has issued the following statement.

NACD Gas Analysis Advisory

NACD National Association for Cave Diving Nitrox Trimix Rosemary E Lunn Roz Lunn The Underwater Marketing Company DAN Safety ReportThe recent death of a cave diver highlights the necessity to review some critical procedures that we should be doing before all dives – gas analysis. A couple of years ago there was a cave diver death in Cozumel that resulted from breathing high carbon monoxide content in a cylinder. This created quite a commotion that caused the sales of CO analyzers to jump quite a bit. These days it’s not uncommon to see divers analyzing their cylinders for CO during the pre-dive process. However, even with that awareness it is a bit surprising that there are still divers that do not analyze all cylinders for oxygen content. While the NACD does not have courses for mixed gas procedures diving at this time, all NACD instructors should be emphasizing the need for gas analysis during the pre-dive process.

Divers should re-analyze all cylinders to be used on a dive at the site during the pre-dive process and make sure the cylinders are properly labeled with oxygen content, helium content (if any helium in the blend), and MOD. This should occur even if the cylinders were personally filled by the diver. Each and every cylinder should be analyzed and clearly labeled, even if there is an isolator connecting the cylinders, and regardless what gas is believed to be in the cylinder.

While it is understood that not everyone may own enough cylinders to permanently mark them with content and MOD, cylinders being used for 100% oxygen should be permanently marked and only used for 100% oxygen. However, permanent markings do not substitute for additional labeling. Even permanently marked cylinders need to be analyzed and labeled with content and MOD to show confirmation of the contents. There should never be any confusion about labeling. It should be clear and concise to anyone who looks at it.

Finally, there is some controversy over whether gas analysis should be an individual responsibility or a team responsibility. All divers with mixed gas training of any kind have been instructed that all gas should personally be analyzed prior to every dive. Almost every dive training class emphasizes gas sharing with teammates. With that, there is always the potential for a diver to be breathing from a teammate’s cylinders. Gas analysis and confirmation should be a team project during the pre-dive process.

The lessons to take away from this:

1. Analyze every cylinder, whether you think it is filled with air, Nitrox, Trimix, or Oxygen,
2. Label every cylinder with gas content and MOD
3. Remove all old, Oxygen, Nitrox, and Custom Mix labels if the cylinder is to be repurposed.
4. Make gas analysis a team project.

If you are unfamiliar with or out of practice with analyzing gas contact any NACD instructor and request a gas analysis refresher. If you do not have an NACD instructor nearby contact the training committee and we will provide you with an instructor who can help you.

Gas analysis is not an optional activity. Your life depends upon it.

Rob Neto
NACD International Training Director
NACD International Safety Officer


Check out the new website National Association for Cave Diving

Kathy Dowsett
www.kirkscubagear.com