Understanding Enriched Air Nitrox

If for example, you plan on performing 4 dives in a day and you want to dive Nitrox on all four dives, performing the deepest dive first, second deepest on your second dive and so on, what mix or blends would you request for your four cylinders?

Let presume the deepest dive will not be deeper than 110 feet. There is a really cool wreck there and you always wanted to check her out. Your second dive is no deeper than 80′, the third 60′ and the last 50′.

The wrong answers are where your PPO exceed 1.4 or a dive hovering close to 1.4 for a prolong period of time.

I can’t provide you with an answer because there are so many with so many conditions and reasons. The thought behind the question is to have you think about what you are planning to dive and how you should be managing it. For example you may ask: How much Oxygen Toxicity will I incur? How much nitrogen will I load? What will be my Residual Nitrogen Times, RNT? What Surface Interval times will I need? What are the depths at the sites we plan to dive?

These are things you may consider when you are in control of all aspects of the dive. When you leave it up to an operator, ie. when you travel and a dive operator decides the sites, the dive times are limited to say 50 minutes, surface intervals are no less than 1 hour and depths are no deeper than 100fsw. You may choose the PPO for your cylinder but most everything else is managed for you.

At this point, you have been introduced to quite a bit of information. Some new, some old yet everything you have been taught led you to this point. The point where you can now begin planning dives using Nitrox.

From here we will be looking at a number of tables provided to help you calculate a dive. Some calculations will require you to use the formulas mentioned earlier and yes, some new formulas because there are no tables for some calculations. That’s on you.

Are you ready?

Here are a few tables you may find divers using. There are many more and these were arbitrarily picked. Since we have been referencing the tables sanctioned by PADI we will continue with those.

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