Central Scotland Dive Club

Diving with Nitrox

Enriched Air Nitrox
– the ideal gas for Scuba Diving?

When you become a qualified diver, you will want to spend as much time underwater as possible. During training, you will learn that the duration of your dive is governed not just by your air consumption, but by your body's absorption of the nitrogen in the air you are breathing under pressure; and the deeper and longer you dive, the more nitrogen your body absorbs.

But what if there was a way to reduce the nitrogen content in your air supply? Well there is, and the result is Enriched Air Nitrox – or simply Nitrox. Its use brings important benefits which, in turn, require additional training and responsibility.

What is Nitrox?

Nitrox is really any mixture of nitrogen and oxygen, but Enriched Air Nitrox for diving is a gas mix with a higher than normal oxygen content. By increasing the oxygen (O2) content, the nitrogen content is reduced. Often, you will see Nitrox referred to as the abbreviation EANx – and the 'x' refers to the percentage of oxygen in the mix.

Normal air has an O2 content of 21%
EAN28 has an O2 content of 28%
EAN32 has an O2 content of 32%
EAN36 has an O2 content of 36%
EAN40 has an O2 content of 40%

Now, you might think "surely, the more oxygen, the better" – but there is a catch, and it's called "oxygen toxicity". On the C-Divers Nitrox Course, you will discover all you need to know about oxygen toxicity and how to avoid it. Briefly though, you will learn that each mix of Nitrox has a "safe*" Maximum Operating Depth, or MOD for short. There are other factors that divers also have to be aware of – and that is why Nitrox must only be supplied to divers who are qualified to use it.

What are the benefits of Diving with Nitrox?

– More time underwater (assuming you have enough gas)
– Shorter surface intervals between dives
– Less exposure to nitrogen absorption

What are the Nitrox Maximum Operating Depths (MODs)?

For a "safe*" maximum O2 partial pressure of 1.4 bar, the following depths apply:

EAN28 has an MOD of 40m
EAN32 has an MOD of 33m
EAN36 has an MOD of 28m
EAN40 has an MOD of 25m

What are the Nitrox Equivalent Air Depths (EADs)?

At a partial pressure of 1.4 bar, the following EADs apply:

EAN28 at 40m has an EAD of 36m
EAN32 at 33m has an EAD of 27m
EAN36 at 28m has an EAD of 21m
EAN40 at 25m has an EAD of 18m

Note: These Equivalent Air Depths are rounded to the approved levels of the SAA Bühlmann System.

Dive Safety and Disclaimer:
Diving is a risk sport and because people vary in their susceptibility to decompression illness, oxygen toxicity and carbon dioxide retention, no set of tables, dive computer or calculations can guarantee your safety and total avoidance of diving related illnesses.

Because of the complex nature of diving, if you use the information on this page or section you take full personal responsibility for your own safety and for any outcome.

Under no circumstances will Central Scotland Dive Club, its members or the Sub Aqua Association be responsible for any consequential damages.

Do not attempt to use any diving tables, calculations, computers or other equipment, without first having taken a formal training course provided by a recognised diver training agency. Never dive beyond the limit of your training and experience without a qualified instructor.