What is Nitrox?

Nitrox is the name commonly given to a breathing gas called Enriched Air Nitrox. By using Nitrox a diver can dive for longer without exceeding their no decompression limits, but what is it and how can you get to use it?

[singlepic id=155 w=320 h=240 float=left]Any mixture of oxygen and nitrogen is actually Nitrox, air could be called normoxic Nitrox if you wanted to get fancy. We usually call a gas Nitrox when the oxygen percentage is over 21%. (The level in air) The two most common blends of the gas are those with 32% (written EAN32)[singlepic id=159 w=320 h=240 float=left] and 36% (EAN36) oxygen but it’s not exactly the oxygen content that makes the difference. The key to the way Nitrox works is by lowering the amount of nitrogen. Without adding another third gas to our tanks the only way to lower the amount of nitrogen is to add more oxygen.

Why lower the nitrogen content? By lowering the content of this gas, we breathe a lower partial pressure of it at depth.


[singlepic id=156 w=320 h=240 float=right]We know that the higher the partial pressure of inert gas we breathe, the faster our tissues take on that inert gas. Over time our tissues absorb this gas to a point where we need to ascend to the surface slowly as we are approaching limits given to us by decompression tables and computers. But when using Nitrox we hit this limit later due to slower ongasing of nitrogen into our body tissues. In a nutshell the less nitrogen we breathe the longer we should have before our dive time is up.

How do we recognize the gas? If you are on a dive boat you may see tanks with large green and yellow bands around them with Enriched Air Nitrox written on them. Tanks have to marked clearly as they have a higher oxygen content. This is important to remember because we cannot breathe gases high in oxygen at deeper depths due to oxygen toxicity. Oxygen toxicity can easily be avoided by staying to established limits of oxygen pressures. Setting our maximum dive depths to match these oxygen limits is easily done and the danger of oxygen toxicity ‘hit’ is avoided.

The higher the percentage of oxygen in the tank, the shallower the dive must be. For example the maximum safe depths with EAN32 and EAN36 are 33m and 28m respectively.


[singlepic id=157 w=320 h=240 float=left]Nitrox Diving sounds complicated at the beginning but once you’re diving with Nitrox, you’ll see that it is pretty simple in fact. How much more time you get on a dive with Nitrox varies but an example would be diving the HTMS Sattukut wreck here in Koh Tao. The deck of the boat is 25m deep, with air in our tanks our dive time could be no more than around 29mins. If we were to use EAN36 (36% oxygen 64% nitrogen) our dive could be up to 50mins, possibly more when using a computer to take advantage of any multilevel aspect of the dive. So you can see by simply putting another tank on our back we get more time to explore the dive sites we love.

It’s worth mentioning; there is no difference in nitrogen narcosis when using Nitrox, you feel the same as you usually do with air. This is because oxygen is also narcotic at depth just like nitrogen. Many people say that they feel less tried after diving with Nitrox as apposed to air, we believe this is due to less silent bubbles in the body after diving with Nitrox rather than the effect of breathing higher oxygen percentages.

To take advantage of this useful tool, you need to take the PADI or SSI Enriched Air Diver Course. This is a one-day course that can include two dives if you wish but it can be done as a ‘dry’ course with just a classroom session.

[singlepic id=158 w=320 h=240 float=right]Here at Sairee Cottage Diving we offer the PADI Nitrox course for 6000THB (150 Euro) with two dives. We also offer the SSI course for 5000THB (125 Euro). During the course you learn more about using the gas and safety measures, analyzing the tanks and then you will go on two deeper dives around 30m to fully see the advantage of more dive time.

We blend our own Nitrox at Sairee Cottage Diving with a top of the range compressor giving incredibly clean gas to breathe. Pure medical grade oxygen is mixed with filtered air using a sensor to monitor the percentage of oxygen going into the tanks.

If you are already a certified Nitrox diver we can offer you FREE Nitrox to use on your dives if you sign up for a 6 or 10 dive package. You will be with a certified Divemaster also using Nitrox so you can enjoy longer dive times.

Interested? Sign up for your Nitrox Diving Course on Koh Tao Now!

For more information on our Nitrox diving course please contact us here.

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