A luxury liveaboard, a helpful crew… but then someone goes and turns off your gas! Story by Advanced Diver Richard Evans.

We’d been on the liveaboard six days and done 18 dives, some of them to 30 or 32m. We’d got used to the routine, where really all we had to do was kit up and dive. Our cylinders were removed and re-filled on the mother ship by the crew; occasionally we had to make some adjustments to the balance of our kit when we got on board the tenders prior to our next dive, but even this got better and better as the week went on and our crew took it upon themselves to make our lives easy.

I dive with my wife who has logged some 85 or so dives, while I’ve been diving for longer and now have more than 850 logged dives, some of them to depths beyond 100m. As a matter of routine – and I will not be rushed over this – we do our buddy check before we enter the water. I guess it’s both the way I was taught and teach and I’ve seen what happens when its omitted. But what I was about to experience was an event that I now know quite a lot about, but hadn’t fully appreciated how easily it can happen and how frightening it can be.

We had completed our buddy check… BCs fastened, weights in place. Our gases were turned on and both the integrated sender / computer and the analogue gauges were reading 200+ bar and breathing fine.

Have you ever breathed a tank dry? Well I have and with it goes an important lesson!

Just before you run dry you feel resistance in the second stage because the gases demanded are flowing less well.
So when after about five minutes into the dive, and at 31m, my second stage gave this feeling of resistance, I knew something was up. I looked to my computer to check my tank pressure: it displayed 186bar. I looked at my analogue gauge. Briefly, it read zero then gradually came back to 186 bar. No time to waste: I struck out with a couple of big fin kicks for my wife, my buddy. She was quite close and I instinctively grabbed the yellow octopus line and second stage. Eureka! I’d got a breathing gas (the same as mine!).

But what had happened? Everything was showing pressure again. Had I dived with an empty cylinder? 

Surely not – it was showing plenty of pressure when we did our check. Was my regulator faulty? Well, why? I’d done 18  dives already, it was serviced within the last three months and had been dived regularly. Had sand entered into the first stage? Had someone been stupid enough to turn my tank off?

My technical training taught me the skill of opening and shutting down cylinder valves during a dive, so that’s what I did. And that’s when I found out what the problem was. My tank valve was only half a turn open!

In shallow water or while doing a buddy check, a partially open valve may be capable of delivering sufficient gas, but at depth it's a different story. The same valve setting can leave the diver starved of breathing gas. I cycled the valve, opened it fully, checked my analogue gauge and checked my computer. It had taken less than one minute, but it felt like ages! My buddy, bless her, had realised my predicament. She had also realised that without breathing gas my buoyancy was zilch! She began to assist me upwards to a shallower depth. A great response from her, especially as the less experienced diver. But we’d practiced such scenarios many times. I switched back to my regulator, somewhat nervously. I checked everything was fine and was confident we had solved the issue – we had and we continued our dive for the remaining 40 minutes.

Now there are lessons here for divers, as well as dive operators.

I always turn my air on before I put the BCD / cylinder on my back. My wife does the same. Breathing gases are the divers' domain and absolutely no-one should interfere with them! This dive operator, as I mentioned, was inclined to do everything for their guests. They had a habit of going around the gunnel of the dive boat checking divers had their air turned on.

Well, they’d turned mine off! It’s important to understand what happened here because it was this unnecessary action that caused the incident.

My advice for dive operators is leave the ‘gas taps’ alone – they are the diver’s responsibility!

My message to divers, to diver operators and to diving instructors is to stop this bad habit; it’s not needed and may endanger someone’s life! To all divers, do a buddy check, and don’t let anyone rush you. Two more minutes will rarely impact on the dive, but may save your, or another diver’s life!

Now read the Incident Analysis for Taking Control: Wrong turn!

Article source - SCUBA magazine issue 64

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