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What is Nitrox?

  • Nitrox is any mix of Nitrogen and Air.

  • Normoxic Nitrox is normal air. (21% Oxygen and 79% Nitrogen)

  • Hyperoxic Nitrox is a mix with more than 21% Oxygen

– Hyperoxic mixes are known as Enriched Air or Enriched Air Nitrox


What is Nitrox?

  • EANx X is the % of Oxygen

  • Safe Air (Refers to a mix between 22% and 50%)

  • SAA has four basic mixes

  • EAN 28 This is 28% Oxygen

  • EAN 32 This is 32% Oxygen

  • EAN 36 This is 36% Oxygen

  • EAN 40 This is 40% Oxygen



Elementary Nitrox

How long has it been around ?

Some experiments done in the 1870’s

1910/1912 various tests done using Nitrox while riding a bike

Lots of work done during the war (lots of progress)

Started to be used as a sports gas in the 1970’s

Elementary Nitrox

  • How do you name a mix ?

  • – Oxygen content always named first
  • EAN32 is 32% Oxygen and therefore 68% Nitrogen.

  • EAN40 would be 40% Oxygen and 60% Nitrogen.


bulletNote both figures must add up to 100%.

Elementary Nitrox

Air is a Nitrox Mix.

Air is 21% O2 and 79% Nitrogen.

All mixes for the Nitrox diver are just air enriched with Oxygen

Elementary Nitrox

Why Use Nitrox?

Nitrox is safer than air if used correctly.

Nitrox reduces the chances of illnesses which are associated with diving.

Nitrox increases the time that can be safely spent underwater.

Elementary Nitrox

• Each mix has a Maximum Operating Depth (MOD)

28% 40 Metres MOD

32% 33 Metres MOD

36% 28 Metres MOD

40% 25 Metres MOD

Elementary Nitrox

  • Equipment Differences

  • You must only use Oxygen in Service cylinders

– Oxygen Clean plus Oxygen Compatible makes equipment in Oxygen Service.

  • Oxygen Compatible means suitable for use with pure oxygen.

  • Oxygen Clean refers to equipment which has been cleaned for use with pure oxygen.

Elementary Nitrox

• Current Cylinder markings for Europe are Black, but tend to be any colour with a “Nitrox Sticker” in black.

Elementary Nitrox

  • All mixes “MUST” be tested prior to use.

  • Mixes are tested using a Gas Analyser

  • Calibrate the Analyser and connect to the cylinder to be tested.

  • Turn on valve and allow a gentle flow of the gas to pass the analyser for about 15 seconds. Log the percentage reading


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