Nitrox was popularized within the recreational scuba diving community in the 1990s. The term nitrox refers to any mixture of gas with a higher percentage of oxygen than you would find in a typical cylinder full of compressed air. The air that we breathe is typically right around 21% oxygen, 78% nitrogen and then 1% other gases.
When a cylinder of gas is marked as Nitrox, you can expect the oxygen content of that mix to be higher than 21%. In most scenarios, specifically in recreational diving, where you see a cylinder that is marked Nitrox, you are going to be looking at a cylinder that contains anywhere from 28-36% oxygen, the rest being a mix of mostly nitrogen and 1% other gas.
Can you dive deeper with Nitrox?
Short answer to this question is no. You will never be able to dive deeper while breathing a traditional nitrox blend. When breathing gas with a higher percentage of oxygen than compressed air, you run the risk of encountering either acute or chronic oxygen toxicity.
Oxygen toxicity is extremely dangerous when underwater and at depth as it can lead to convulsions, even without any symptoms popping up beforehand. There is a really high chance that if you convulse while at depth that you will lose your regulator and drown.
When should you use Nitrox?
Using nitrox can give a handful of benefits to divers that choose to dive nitrox, as long as they do so safely. These are a few of the situations where using nitrox can make more sense than breathing air:
- You are prone to decompression sickness
- You have taken previous DCS hits
- Your bottom time is starting to become limited more by your NDL limits than it is by your gas remaining
- You want to dive more conservatively and stay safely within NDL limits
Using nitrox in these situations can provide a safer experience to divers trained to dive with enriched air nitrox. For example, if you plan a dive to 90 feet and are going to be breathing regular air, according to PADI’s Recreational Dive Planner your max time before you would need decompression would be 25 minutes. Diving to the same depth on a EANx36 (36% oxygen nitrox mix) your maximum dive time before hitting your no decompression limit extends to 40 minutes.
If you dive conservatively and well within limits, nitrox can give you a ton of benefits when you choose to dive with it. Just always remember to stay well within your Maximum Operating Depth, and never push your NDL limit unless you are trained to do so and have a deco plan in place prior to the dive.
How deep can you go with nitrox?
This is a tricky question. Because nitrox is any mix of gas with a higher percentage of oxygen than 21%, the answer is going to vary greatly. Most commonly in dive shops and on dive boats, you are going to see EANx32 (32% oxygen). With EANx32, your maximum operating depth is going to be 121ft. Another common mix of nitrox for recreational diving is 36% oxygen, with which you can safely dive to about 100ft.
If you are wondering what blend you will need for the depth that you plan on diving, you can typically find a MOD table in whichever shop you have filling your tanks. Most of the time a MOD table is going to look like this:
Does diving with Nitrox improve your air consumption rate?
The short answer to this is that generally no, any effect on your air consumption rate stemming directly from the gas in your cylinder being nitrox will be negligible. It is pretty safe to say that you are going to breathe your gas at the same rate as you would if it were just compressed air.
There are some divers who experience a better air consumption rate while diving with nitrox as opposed to air, but it is not a general rule of thumb that nitrox will give a diver a better air consumption rate automatically.
How much does a Nitrox certification cost?
This is going to vary from dive shop to dive shop and also from certifying agency to certifying agency, but most of the time you can get a basic nitrox certification for under $200. The most common dive agency, at least here in the United States, is going to be PADI. PADI offers their enriched air diver certification course to anyone that has at least an Open Water Diver certification through their agency, or an equivalent certification from another agency such as SSI. PADI offers an online learning platform for enriched air, and the cost is $180 at the time of writing this article.
How do you know how much oxygen is in your tank of nitrox?
After being certified with a basic nitrox certification, you will be able to get tanks filled at any dive shop that fills nitrox for blends of up to 40% oxygen. While most of the time you are going to get a blend of gas that you ask for from the shop, it is required that you test your own tank to verify the blend of gas that is in the tank.
Most dive shops will allow you to use their oxygen analyzer while in the shop to confirm that the tank is filled up with the blend of gas that was put into the cylinder. You will want to perform this check before you sign the fill station log book, as at that point the tank and its contents are your responsibility, not the dive shops.