Top 25 Dive Travel Questions, #21, What is Nitrox Diving?

by: admin
July 9, 2010

Nitrox.   What is it? Do I need it?   Where can I get it?

Nitrox (or EANx Enriched Air Nitrox) has become a part of mainstream recreational diving over the past 10-15 years. Yet there are many divers who do not yet understand what it is or when or how to use it.

Nitrox is essentially Enriched Air which means that oxygen is added to “regular” air.   Regular air contains about 21% oxygen and 79% nitrogen.   By having, for example 32% of your air O2, you reduce the amount of nitrogen coming into your system, thus allowing you longer bottom time within a particular range of depths.

Common Questions about Nitrox

Isn’t Nitrox for Deep Diving?

No.   Nitrox was designed to give you longer bottom times at intermediate depths and reduce surface intervals.   This is very confusing to many people.   It was not intended for deep depths as oxygen becomes toxic at higher partial pressures. So the more oxygen you have in your mix the shallower your gas will become toxic.     So, depending on your mix (standards are 32% or 36%) Nitrox is ideal for the   50-110 ft range which is the range in which most recreational diving is done.

Will Nitrox allow me to stay down longer?

Here is another very confusing part about Nitrox for many people.   Nitrox does not affect your air consumption in the way that a larger tank or better fitness or better underwater trim will.   Nitrox will “give you” more bottom time at a particular depth.   Say your air computer is showing 20 minutes of NDL at 70 feet partway through your dive.   Using Nitrox you may be able to stay at 70 feet for 30 minutes.   Whether or not you have the air capacity to do that is a different story.   Do note, that if your computer allows you longer bottom time at a depth, you may choose to stay longer.   If you do, you will use more air due to the deeper depth you’ve chosen to dive.

Do I need a special Computer to Dive Nitrox?

Yes and No. The computer must be able to do the calculations using a gas that is not mixed at 21% if you want to get the benefits of diving with Nitrox.   However, if you dive on Nitrox with your computer set at 21% (providing your mix is 22% or greater) you will simply add a higher element of safety.   However, you need to be VERY aware of your MOD.

What is an MOD?

Because oxygen becomes toxic at depth, when you have a higher % of oxygen in your gas mix, it is important to understand that you will have a shallower maximum depth allowance.   MOD stands for Maximum Operating Depth.   For any blend of enriched air, it is ESSENTIAL that you know and stick to the limits of the operating depth for that gas.
I recommend you stay well within your MOD and that you also set a depth alarm indicator on your computer about five feet shallower than your MOD to give you an audible warning.

Do I need Certification to Dive with Nitrox?

top 25 dive travel questions

A typical certification card for Nitrox

Yes. You need to be certified to dive with Nitrox and have your Nitrox certification card with you if you expect to use it.   Many resorts offer training in Nitrox though it is usually less expensive to do it at home at your local dive shop.   Global Dive will do your certification on an adventure free of charge, you just pay for your materials and fills.   Not every resort is able to provide Nitrox due to difficulties of getting pure oxygen at many remote locations so ask ahead of time.   Also, expect to pay up to $15/dive extra for your Nitrox fills.   Some live aboards offer Nitrox included in the price of the trip or free if you are a repeat guest on board.   Always ask.

A VERY important thing to be sure of is that the resort has a working Nitrox analyzer.   You need to analyze YOUR OWN fill before a dive and sign off on a log.   If they do not have a working analyzer DO NOT dive with Nitrox.   You can always purchase and carry your own analyzer.

To Your Adventures!

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