Nitrox/Enriched Air Do you Need it?

The Nitrox/enriched air certification is probably the most common specialty certifications that divers get, it is quick and easy all classroom no required dives, and can be completed in an hour or 2. But I think a lot of divers are oversold and misunderstand Nitrox. This post is meant to talk about some of the benefits and uses of Nitrox and some of the misconceptions. Hopefully to help new divers make a more informed decision about if getting Nitrox certified is worth their while.

  • What is Nitrox/Enriched air? To put it simply Nitrox is any mixture of air where the percentage of Oxygen is above 21%. Most of the time the standard mixes for Nitrox are 32% and 36%, 32 being the most common.
  • What is the benefit of a higher percentage of oxygen? By increasing the oxygen in the air it reduces the percentage of nitrogen, this means that while diving the divers body will absorb less nitrogen.
  • What is the advantage of less Nitrogen absorption? Certified divers will know that during a normal dive breathing compressed air our bodies absorb nitrogen into our different tissues and this takes time for the nitrogen to work its way out. During the dive we keep track of our No Decompression time (this is an estimate of nitrogen absorption based on our depth and time underwater) the deeper you go and the longer you stay underwater the more nitrogen our body absorbs. This nitrogen can get trapped in the body in some circumstances causing Decompression sickness or the “bends” caused by nitrogen bubbles expanding during ascent and getting stuck. So by reducing the amount of nitrogen in the gas we are breathing we reduce the amount of nitrogen we absorb on a dive. This extends our potential No Decompression time while diving. In addition to potential longer No Deco times the time between dives “surface interval” is shortened because there is less nitrogen for our body to off gas after the dive before we begin the next dive.
  • When is Nitrox Useful? Nitrox is most useful when divers are completing multiple dives in short durations, like of dive trips where somebody might do 2-4 dives in a day over multiple days in a row.
  • Additional benefits to Nitrox. Another common reason for divers to prefer Nitrox is because it tends to reduce the amount of fatigue after diving, the built up nitrogen after diving generally causes fatigue and many divers claim that diving Nitrox especially on repetitive dives reduces this feeling. Nitrox tends to be a popular option for older divers that are more affected by fatigue, because of this it has gained the nickname “Geezer Gas”

Common Misconceptions about Nitrox.

  • You can dive longer on Nitrox. This is something I hear generally from new divers or people that are being sold the benefits of Nitrox. Yes you will have more No Deco time while diving on nitrox but you will still consume air at the same rate as regular air. So you do have the potential to dive longer but if you are looking for a solution to being an air hog underwater Nitrox will not make a difference to your actual dive time.
  • You can dive deeper. This is something divers that have not been Nitrox certified believe, because of the increased percentage of oxygen in Nitrox your max depth is actually reduced for a standard 32% Nitrox blend your max depth is reduced to about 110 ft instead of your recreational max of 140ft on regular air. This is due to the potential for oxygen toxicity due to the higher concentration of oxygen at depth. So as you increase the percentage of oxygen in the blend the shallower your maximum depth is.
  • You can fill any tank with Nitrox. Yes any new tank can be filled with nitrox but those tanks should be clearly marked Nitrox only with a large green and yellow sticker (in the US). Because oxygen supports combustion, contaminants must be cleaned from tanks before filling with oxygen, there are different methods of filling tanks for Nitrox a common method is Partial pressure blending were a tank is filled to a calculated pressure with air then pure oxygen is filled to increase the percentage, because pure oxygen is being filled into the tank there is a combustion hazard if the tank is not filled. With this being said tanks that are not marked for Nitrox or have not been O2 cleaned should not be used to fill with Nitrox.

In my opinion for most divers Nitrox isn’t really necessary, of course it depends on the circumstances of the dives/trip and there are situations where it is called for. When should you consider Nitrox, trips with multiple days of diving with multiple dives a day, preferably shallower dives, or if you feel extreme fatigue after diving. When is it not necessary for deeper dives, single tank dives, or most single day diving excursions.

I always find it funny to see people diving in cold water with Nitrox tanks, especially at training sites that don’t get deeper than 50ft and you can see the entire site in under 1 hour, most of the time it is not the deco time that is affecting the length of the dive it is body temperature and air consumption, two things Nitrox has no effect on. The other thing to keep in mind is that obviously because of the process to fill Nitrox it is more expensive to get Nitrox fills or rent Nitrox tanks, so people are paying more for the sake of paying more. So I find it unnecessary for most cold water diving situations. It is common to see instructors teaching classes using nitrox and this I can only assume is a sales techniques to convince students to take the class.

So finally, should you get Nitrox certified? If you think the benefits will be to your advantage then yes. It is a short class that is usually pretty inexpensive compared to other specialty classes so if it is something you think you will use go for it, but it probably won’t have as drastic effect on your diving as your instructor may be selling you.


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