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Is there any special equipment needed for diving with Nitrox(more than 21% O2)? In Germany there are regulations and laws that say that you can only dive using Nitrox if you have this special equipment. I did my SSI Nitrox diver in Indonesia, where we used the regular equipment. Also, I've nowhere before heard of this special equipment. Does anyone have experience with this special equipment? And if so, what is it exactly and what does it cost?

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Yes, and no, it kind of depends on the local laws.

So long as your equipment is covered by your manufacturer guarantee, and you will have to bear in mind as will all diving the local laws and legislations for equipment use in various countries / regions within a country, then it can use a higher FO2 than diving with Air.

However your equipment must be:

  1. Oxygen Clean*.
  2. Use Oxygen Compatible Air.
  3. Be serviced regularly. (I believe with SSI they're making this more frequent)

Specialist Equipment in this sense is where you have separate equipment which does not use regular Air or other mixes. This will be things like:

  1. O rings.
  2. Cylinders.
  3. Regs (first and second stages), etc.

Consider this as having a separate breathing system for higher FO2 mixes.

In some cases this can be your usual equipment after a service + oxygen cleaning. Cost varies.

This information is covered in the SSI Nitrox 32% and 40% courses (at least as of November 2016 for a certainty as that's when I did this course myself).

*Oxygen cleaning is a chemical cleaning, surface preparation service for products intended for use in oxygen. - in short, this is to remove particles etc from your gear, it also means you use oxygen compatible sealants, chemicals etc on the equipment as otherwise friction can cause fire and/or explosions due to the high pressures.

  • If breathing up to 40% (i.e. not the very rich O2 concentrations found in decompression gasses), your regulators do not need to be specially O2 cleaned and certified. Only the cylinders need to be as they may be exposed to very high concentrations of O2 when filling -- it is very common to put pure O2 into dive cylinders then top-off with clean air. – GlennG Jan 23 '17 at 23:26
  • @GlennG this may depend on your dive store and who you study with - I did the up to 40% Nitrox course with SSI Nov 2016 and they stated that you do need to O2 clean anything that comes into contact with the higher FO2 gases. – Aravona Feb 8 '17 at 8:57
  • That's different from other agencies and the actual requirements. Might be that they're being particularly risk averse and strict (or selling O2 cleaning services??). Regulators aren't exposed to very high concentrations of O2 within recreational Nitrox use (i.e. up to 40%). However the cylinders & valves will need to be O2 cleaned as they're commonly filled with pure O2 and topped off (diluted) with clean air -- example: an empty cylinder requiring 32% will need 32bar of pure O2 and topped off to 232bar with clean air. – GlennG Feb 8 '17 at 10:18
  • Your first stage reg should still be O2 cleaned, and since you have HP ports on them then this would need O2 maintenance. Yes, SSI are a lot stricter than most, but you may or may not need to do your second depending on what your FO2 is - it maybe outside the remit of recreational diving and onto technical. The main thing is to always follow local area and manufacturer regulations. – Aravona Feb 8 '17 at 10:56
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    One thing to keep in mind is that certain types of O-rings can degrade faster or otherwise react poorly with oxygen rich air. Your best bet is to talk with your regulator technician at your dive shop and see what they recommend. – Malco Apr 6 '17 at 17:13
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The "special equipment" needed for Nitrox most likely refers to the M26 tank valve fitting, which in certain European countries replaces the classic 5/8" DIN valve for cylinders that are for use with Nitrox (oxygen clean, etc). They are much larger and so a DIN regulator first stage cannot be screwed in, meaning you need special regs for Nitrox too. However most of the world ignored M26 and continues to use the same DIN valve (with or without an insert) for both air and Nitrox. Adaptors between the two standards are available, expect to pay around £20.

  • You can use DIN regs with O2. – Aravona Jun 29 '18 at 10:11
  • ... because most of the world ignored M26... – gaius Jun 29 '18 at 11:57
  • Yeah, not even heard of that in the UK, everywhere I dive is DIN - the only adaptor I've been warned to get is for Yolk if diving in the US. Perhaps a link as I can't even find it only for an example? – Aravona Jun 29 '18 at 12:26
  • If you are extremely interested you can purchase a copy of the relevant standard here shop.bsigroup.com/ProductDetail/?pid=000000000030110092 - it costs considerably more than an adaptor! – gaius Jun 30 '18 at 6:29
  • I meant more to expand your answer with what the M26 valve looks like :) – Aravona Jul 2 '18 at 7:44
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The main 'special equipment' is to have an O2 analyser and use it. You should also have waterproof tape (Gaffa tape) and marker pen.

Cylinders should be O2 cleaned according to local regulations (every 15 months in the UK). Regulators don't need to be specialist O2-compatible devices (for example the green ones sold for twice the price of normal regulators). Note that some (expensive) titanium regulators are not recommended for use with 100% oxygen.

Mark up your cylinders with tape on the cylinder neck with the analysed O2 percentage to one decimal place and the date.

Some agencies require the MOD (Max. Operating Depth)

MOD = (1.4 / O2_fraction) - 1

Example: MOD of 32% in metres:

MOD = (1.4 / 0.32) - 1
    = 4.375 - 1
    = 33.75 metres

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