Understand your breathing gas at all times…

..this something drummed into CCR divers all the time. The same applies to OC divers too.

I recently found this 1996 accident report whilst doing my PhD literature review for diving incident causality factors – https://www.mja.com.au/journal/1996/165/5/diving-fatality-due-oxygen-toxicity-during – which concerned a diver with a cylinder of air and a cylinder of 50% with a switch block which allowed the gas to be switched over during the dive.  Unfortunately, the diver died after a OxTox event; either because he accidentally knocked the valve or intentionally switched it but at the wrong depth because he was narc’d at 47m on air.

Gas Cylinders with Trimix and 50%


That report was 18 years ago.

This image was sent to me last year and you can see that this diver has an interesting combination of gases. The amount of gas consumed in the left cylinder will determine what the final mixed gas will be if the manifold is opened, for whatever reason. Donating gas from the right cylinder at depth may have fatal consequences too…

Know what you are breathing at all times! If you are on a CCR analyse the gases before you connect the 1st stages, and then use the handset/HUD during the dive, if you are on OC make sure you analyse your gas before you attach the regs. In both cases, doesn’t matter if you have decanted the gas yourself, you can and will make mistakes. 2 mins may save your life…

One response to “Understand your breathing gas at all times…

  1. Pingback: Following on from the fatal at Ginnie Springs·

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