What is Nitrox?

If you have recently started scuba diving you have probably heard the word Nitrox, or perhaps seen it being used by other divers on your dive boats. Those yellow and green bands sure are hard to miss! So presumably by now you may have the question, “What is Nitrox?” circling in your mind, and hence you found your way to our blog. While we could get all technical and try to give you a quick lesson on Nitrox, we have decided to break this down into simple terms in a real-world application scenario. We’ll save the technical stuff for the classroom.

Life without Nitrox

I can remember my first dives on the C-53 wreck in Cozumel. This was long ago, prior to my professional career and, more importantly on this dive, before I was nitrox certified. On this dive I remember the underwater visibility was amazing and the shipwreck itself was teeming with vibrant marine life. This was my first wreck dive ever and I was instantly hooked! However, my dives were cut short that day. The Divemaster for that dive had me surface long before I ran out of air. I was confused and disappointed.

Back in those days I was not diving with a computer. Not to date myself, but dive computers were not yet mainstream. So, when my Divemaster signalled for me to surface, I was not really sure what was going on. Once on the boat my Divemaster tried to explain to me something about “no decompression limits” and “not using nitrox” but all I remember was being confused and still focused on my disappoint from missing those precious minutes on that incredible dive.

How Does Nitrox Help?

As you would have learned in your Open Water course, our body absorbs the non-required gas Nitrogen while we are underwater. And thus, the time we can spend enjoying this amazing underwater world is majorly limited by the absorption of Nitrogen by our body. Since its a non-required gas for our body, we can safely absorb only a limited amount of Nitrogen before we must slowly ascend and finish our dives.

However, with Enriched Air Nitrox, because of the increased Oxygen percentage and thereby reduced Nitrogen percentage in our breathing gas mixture, we can significantly change the amount of time we can spend underwater. Less Nitrogen in our cylinders results in less Nitrogen absorbed by our bodies giving us more time underwater! Sounds simple, right?!

Nitrox dive computer test

Nitrox in Practice


I could keep trying to explain this to you, or I can simply show it to you. What we did was take down two Mares Puck dive computers side-by-side and take some photographs during a normal dive. The dive computer on the left is configured for 21% air (normal breathing gas), while the computer on the right is configured for Enriched Air Nitrox 32%. Martin our Divemaster is our diver, while he was leading normal dives for our guests.

This first photo shows both computers before entering the water. The computer on the left, as it is in AIR mode, shows the surrounding air temperature of 92 degrees Fahrenheit. The computer on the right, as it is in EAN mode, shows 32%. Okay… Let’s go diving!

Nitrox Test Begins


Now 17 minutes into the dive, we can clearly see, the “No Decompression Limit” (aka NDL) time of 44 minutes in the Nitrox computer is exactly double of the “No Deco” time in the Air computer. Both computers have been into the dive for 17 minutes and both are at 67 feet depth. Okay, so one photo 17 minutes into a dive should immediately create a clear picture for you but let’s not stop yet. We still got dive time remaining!

Nitrox dive computer test
Dive Computer testing

Nitrox Starts to Show


Third photo, now 40 minutes into the dive. The Nitrox computer still allowing the diver 22 minutes at 70 feet of NDL. In comparison, if diving with Air, with just 4 minutes of “No Decompression” time left, you will be forced to ascend and head towards your safety stop. But wait, there is more…

First, remember this is a highly trained dive professional making this dive for us. Second, they are also using 32% nitrox. So, they are well within their safety margin. But let’s take a look at the AIR computer and what happens to it in the next few photos.

Nitrox for the Win!


What these next few photos will show you is, if you were continuing your dive with Air, you would have already broken one of the Golden Rules of recreational diving about No Decompression Time Limits – Do Not Exceed your NDL. We can see this on our AIR mode computer. While Martin did ascend slightly to 60 feet at the 44 minute mark, the AIR mode computer is already in Decompression procedures.

However, in direct contrast, the 32% Nitrox computer says you can safely enjoy the underwater world for an additional 24 minutes.

Dive Computer testing
Dive Computer testing

Just Say No! to Deco Mode


As Martin slowly ascends to 52 feet, the discrepancy grows. Now 35 minutes of remaining no-decompression time remains with Nitrox…

But with our Air computer in Decompression Diving mode, we have effectively exited recreational scuba diving. Following proper dive protocols, our diving for today is now theoretically over. Or at least it would be if we were diving on 21% air. But thankfully Martin is diving with 32% and will continue with three additional dives today.


On the Safety Stop


Finally, Martin has ascended to his 3-minute Safety Stop. This photo hammers home the safety aspect of Enriched Air Nitrox. With Nitrox, we are showing 65 minutes of bottom time remaining. In stark contrast, we have 4 minutes of Decompression time, 3 minutes of Safety Stop time, and an end-of-day diving situation with Air.

We all love nitrox

Is Nitrox A Magic Gas?

Not quite magic, but close! Despite its many benefits, Enriched Air Nitrox requires knowledge about increased Oxygen percentages and its impact on our bodies. Higher oxygen percentage in our breathing gas has some associated risks as you go deeper. It requires careful planning to ensure we have the right mixture of Nitrogen and Oxygen to get the most out of our dives without risking our safety.

When used correctly, Enriched Air Nitrox is safer than diving normal air. However, when used improperly, Enriched Air Nitrox can potentially injure or kill the diver. Therefore, it is vital to receive instruction from an authorized dive professional.

The SSI Enriched Air Nitrox Course Level 1 eLearning will teach you how to safely plan and dive with Oxygen mixtures of up to 32%. If you are diving with us, you can complete the digital study material on the flight to Cozumel and finish the course dives with us. When completing the class with us including the dives, you will earn the SSI Enriched Air Nitrox Level 2 certification.

Learn more about Enriched Air Nitrox!