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Is 50 Bar Enough?

written by Lee Johnson – Perth Scuba Manager

Decompression Procedures Truk Lagoon, Micronesia

Image by Joey Pool

A few recent diving incidents in Western Australia (early 2013) had me wondering that whilst some diving related incidents and accidents can be attributed to equipment failure and dive site conditions and locations, how many incidents could be prevented with a little more forward thinking when it comes to diver training.

Right from our very first diving experience we were told that there is a number one rule in diving – never hold your breath. Fair enough considering the result of an ascent whilst doing so is usually somewhere in the vicinity of an AGE (Arterial Gas Embolism) and if you are very lucky, a forced air exit (dependant on whether you are looking upwards during the ascent opening your airway to allow forced air out of your lungs – out of your mouth involuntarily). Either way – this type of ascent will generally also come with a package deal of a trip to your local recompression chamber to treat the bend you got on that rapid ascent. But this is not the reason for this article. It’s about something we hear from our instructors from day 1. It’s in some of the reading materials, on the DVDs and on the online training aids we use… It’s the 50 bar rule. 
How many times have you been on a boat full of new divers (Open water dive courses), when the boat Dive Master during his briefing states that everyone must return to the boat with 50 bar? I have heard it a million times and to me, an experienced diver – it is just a standard part of the brief that you always hear. But for the new students, it’s gospel. Almost like the never hold your breath rule… What happens if we come up with less than 50 bar? No one dare ever find out.

I go back a few years now to a diving experience I had with a regular diver from a dive store I once worked at. The dive was nothing special or out of the ordinary apart from the fact that on this particular dive we were hunting Crayfish and had been doing just ok until we went into a cave which had the mother load of Crayfish in it. There were at least 50 of them and they were all good sized Crays. There was nowhere for them to go except our catch bags! I began the selective capture and started putting them into my bag one by one. All of a sudden I had a tug on my fin. A fairly strong one – enough to make me turn around quickly to see what was going on. There was my buddy – wide eyed with gauge in hand pointing at it as if it was about to explode. Thinking the worst (that he had run out of air), I immediately grabbed my Occy and prepared to give it to him whilst looking at his gauge… The gauge read 60 bar. I signalled OK back to my buddy and went back to retrieve my dive torch which I had left behind during the commotion – as I turned away from my buddy, he grabbed my leg and pulled me backwards almost dislodging my regulator and in the process tearing my catch bag off my BCD. I looked around again this time believing that there must be something REALLY wrong with my buddy’s gauge and that he had in fact run out of air. I turned just in time to see my buddy bolting out of the cave and to the surface… I couldn’t catch him and to be honest, I wasn’t going to risk getting bent in an unsuccessful attempt to catch him. I watched him disappear out of view and I slowly ascended. I soon spotted him and saw that he was swimming back towards the boat on his back. When I finally hit the surface I asked him what was wrong – to which he replied “you idiot! We have to be back at the boat with 50 bar!” I paused for a second before replying making sure I deleted the expletives and making sure I said what I wanted to without offending him. Did he honestly believe that it was better to panic and risk a bend with a high speed ascent and no safety stop than to get back to the boat with less than 50 bar??!…. Yes… He did!

Back to present day and owning my own dive store now – I get the privilege of hearing many more briefings and the 50 bar warning is still there in all of them. One of the incidents that occurred in WA a few months back on a bad weekend for dive related incidents, involved a diver who had fairly limited experience and was in general terms new to diving – they had done just a couple of dives since their Open water course but loved diving. The diver was with her buddy at 18 metres when she glanced at her gauge and suddenly bolted to the surface 40 minutes into a dive which had in majority been at 18 metres.

Image by Joey Pool

Image by Joey Pool

There was no stop, no slowing of ascent speed, just a rapid bolt to the surface. On the surface she became disoriented and was in and out of consciousness. Knowing that it was a serious incident the boat crew immediately put the diver on O2 and began treating her for a bend. She was taken to the Rottnest Island medical post and flown to Fremantle hospital by helicopter for treatment in the chamber where she would later make a full recovery (well – as full as can be expected for a bend). Upon investigation what went wrong and expecting to see an empty cylinder, the staff crew were surprised to see that there was still 45 bar in the cylinder! When quizzed later about the ascent she replied “The Dive Master said we “MUST RETURN WITH NO LESS THAN 50 BAR”.

So here we had another incident – only where a diver had actually become bent this time – instead of facing the wrath of the Dive Master who said that everyone must have 50 bar when they get back onto the boat.
I started to ask around and was shocked at what I found. Apparently, some of the Dive Masters in Melbourne tell you if you come up with less than 50 bar you will be stopped from diving again that day and one of my interstate colleagues even said that on one particular vessel they tell you – come up with less than 50 and you won’t be welcome on their boat again. This is in the briefing! Ok, I can see the need to make sure that divers are checking their air regularly and are conscious of how much air they have remaining at all times, but is this worth losing the life of a diver for? If we tell our students and fellow divers that coming back with less than 50 bar is the ultimate sin – then how the hell can we expect new divers or divers with situations that do occur from time to time, to think that a safe ascent is more important? I think it’s about time we address the 50 bar issue with a bit more of a common sense approach. Let’s call it the “Safety margin of 50 bar”. Explain that it is preferred that divers return with 50 bar in their cylinders but if there is an emergency, then complete all stops safely before surfacing. Explaining that this is a safety margin gives the divers the confidence in knowing what we all know… 50 bar is a lot of air and is well sufficient to make a safe ascent from any recreational dive if the dive has been performed within the dive plan – if there has been a miscalculation of air use and 50 bar has been reached.

I have now implemented with my instructors, the need to explain to student divers that the 50 bar “safety margin” is the preferred return to surface pressure, but only if it can be done safely. Before those of you who are about to start criticising this article start with the “irresponsible comment” remarks, please think about it for a second. I can tell you now that we have not and will not ever have an incident like the ones I have mentioned here occur with our divers as they are all in full understanding that it’s the ascent that will kill you not the Dive Master on the boat. They are reminded that the Safety 50 is not a reserve to use at will – it is there for emergency only. I’d rather run the risk of a diver staying for 5 bar more than come up like an Exocet Missile and ultimately putting themselves and others at serious risk.

Let’s have a think about what we tell our most impressionable people at the time when they are at their most vulnerable. They don’t know what we do… Some things are just lost in translation… Ask around what your fellow diver’s think of the 50 bar rule and how they interpret it… You too may be surprised at the response.


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