Lesson 108

Lesson five: Oxygen Issues

Course Complete

We will talk about Oxygen

By the end of this section, I should be able to answer these questions:

1. How do I prevent problems with oxygen when diving with air?

2. Why shouldn’t I dive with a cylinder labeled “oxygen” or known to be filled with 100 percent oxygen?

3. Why is it important to be trained as a PADI Enriched Air Diver, or under the supervision of a PADI Enriched Air Instructor, before attempting to dive with enriched air?

Oxygen Issues

Although we need oxygen to live, under high pressure, oxygen is toxic. If a gas has oxygen in it, oxygen toxicity can result from breathing it deeper than a specific depth. The higher the oxygen content, the shallower the limit for using it while diving. High oxygen percentages can also create some fire/combustion risks with respect to the equipment with which it must be used.

Fortunately, none of these are meaningful issues when breathing air within recreational depth limits.

To avoid oxygen toxicity when diving with air, don’t exceed the maximum depth for recreational diving (40 metres/130 feet).
Fire/combustion problems aren’t issues when using air with standard scuba equipment.

If a diver uses a breathing gas with more than 21 percent oxygen, then the oxygen in it can be toxic at shallower depths. The limit for pure (100 percent) oxygen is only 6 metres/20 feet – any deeper, it is toxic.

Recreational divers don’t use 100 percent oxygen, but tec divers often do (shallower than 6 metres/20 feet, as part of their ascent procedures). They are trained to do this, and also to use equipment that is oxygen service-rated when they do. As a recreational diver, never dive with a scuba cylinder labeled “oxygen” – these are used only by properly trained tec and rebreather divers (you can learn more about rebreather technology in the PADI Rebreather Diver course).

As you learned earlier, enriched air (EANx) has more than 21 percent oxygen. To avoid oxygen toxicity, the maximum depth at which you use enriched air is shallower than when diving with air. How much shallower depends upon how much oxygen the enriched air has.

Enriched air also has some equipment-related concerns associated with the higher oxygen content. It isn’t difficult to avoid oxygen toxicity and equipment-related problems, but it’s necessary to learn how to do so and become certified as a PADI Enriched Air Diver in the PADI Enriched Air Diver course, or to be under the supervision of a PADI Enriched Air Instructor, before diving with enriched air. Otherwise, never dive with a cylinder labeled “Nitrox,” “EANx” or “Enriched Air Nitrox.”

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