14 Aug, 07

The EU have apparently decided that Nitrox and Trimix tanks should have a different cylinder valve from those which can just be filled with air. This valve will be similar to, but incompatible with, existing DIN fittings.

A British diver has started a Downing Street petition against this.
If you’re UK citizen or resident, you can sign up to the petition at� :http://petitions.pm.gov.uk/SCUBA-valves/. The closing date is 28^th September 2007.
Even the HSE opposed this new “standard”, which seems to have the sole purpose of selling more cylinders.
Now, I’m not against the EU in general, but this “standard” is stupid, inconvenient, expensive and – worst of all – downright dangerous.
Apparently, there are also petitions in from French, Slovenian, Czech and Portuguese divers.

So why is this so dumb ? (I’m just going to deal with Nitrox now, as it’s the most widely used of the gas – and the one I’m certified on)

Well, to start off with, the diving agencies are trying to promote Nitrox (and – to a lesser extent – trimix) as safer gases. It seems fairly well established that – when used properly – they are.

BSAC are now introducing (limited) Nitrox certification in its entry-level certification.
By making it more difficult to switch between air and these Nitrox, that means that fewer divers will try Nitrox, which in turn means a potentially greater incidence of DCI (aka “the bends”).

The new measures may mean that these new, safer diving practices may be stillborn.

Nitrox is not available at all fill stations.
So – if the new regulations are implemented – you could be at a dive site with a cylinder you can’t get filled, even if you have a personal filter to ensure the tank’s not contaminated.

Cost factors

Now, this all could cost a fortune.
It currently costs about £25 to test a tank (every 2½ years), and about the same for it to be O² cleaned (every year).
Regulators cost about £50 each to service, and I have four. If I need to double-up on regs, that’s another £800 to buy a couple of sets, and another £100 / year to service.
I regularly switch regs between different tanks, according to the requirements of the dive, so there’s a risk that you’re going to end up on a boat with regs that don’t match the tank….
And that’s without all of the people who buy the wrong type of regulator – or cylinder by mistake (this has already reportedly happened, even though the regs don’t apply yet).

Standards, standards

Regulator fitting “standards” are already a mess, with the A-clamp used in the US, one of the two (existing) DIN standards in Germany, and a mix of the two in most other countries. This is just going to make the whole thing even messier.

Apparently the new fitting resembles, but is not compatible with, the existing DIN fitting. Just what you need … something that looks like it ought to fit, when you’re rocking in a RIB 10 miles offshore ….

So what are the risks that this is trying to avert anyway ?

Risks to divers

The main risk to a diver from Nitrox is that they’ll exceed the “Maximum Operating Depth” (MOD) for the gas mix.

However, in this context, 21% (the proportion of oxygen in air) is just another mix. There’s no “magic” about this proportion. It’s a just a number, which happens to be the ratio of oxygen to nitrogen in our atmosphere at the moment.

Divers training on Nitrox are taught to test their gases.
They have to provide evidence of their training, and to sign a register for each tank of gas they receive.

There’s no evidence that exceeding the MOD is a common cause of diving incidents.

Risks to gas mixers

There is, admittedly, a greater risk to the people at the gas fill stations.

This is mainly because (in most cases) they’re dealing with pure oxygen, with which the cylinder is primed before being topped up with air. If O² comes into contact with combustibles (such as hydrocarbons) then the results can be … well … undesirable.

This is why fill stations are regulated (by IDEST).

For this reason, tanks to be used for Nitrox must be cleaned every year. They are clearly labelled, and won’t be filled with Nitrox after the expiry date.

A different method (for up to 40% Nitrox) is a “membrane” system; these are just starting to find their way into the UK, although they’re common abroad (particularly on Liveaboard boats, where carrying pure O² is impractical and risky). These work by filtering out Nitrogen, rather than adding Oxygen.

The advantage of these are that the tanks don’t really need to be cleaned, as there’s no risk from pure O².

On the other hand, a Nitrox tank may be filled with “clean” (filtered) air. This means that the cylinder is not contaminated for future Nitrox fills.

So … we may have a tank which needs to be “clean” which is filled with 21%, or a tank which can contain 40% Nitrox which doesn’t actually really need to be clean.

The proposed standard doesn’t mitigate risks to divers or to gas mixers. It just makes everything more complicated, difficult and expensive.

So who gains out of this ?
Well, only the tank manufacturers and service centres, really.

Background info :
Wikipedia� Diving Cylinders
Wikipedia – Nitrox

Powered by ScribeFire.

This entry was posted on Tuesday, August 14th, 2007 at 1:16 am and is filed under Assorted rants. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.