The Ean40 Limit

Why am I Limited to EAN40?

Recreational divers are trained to use enriched air up to EAN40. This is because most dive equipment like cylinders, tank valves, regulators, and SPGs can be used with up to 40% oxygen without modification or implementation of special cleaning procedures. While some regulators like the Atomic M1 are actually rated above EAN40, but this is more of a consideration for technical divers than recreational divers.

There are several reasons why blends greater than 40 percent are considered outside the range of recreational diving. First, whenever we use a blend higher than EAN40, several serious equipment issues come into play. Oxygen is highly combustable. Even the smallest trace of a contaminant can ignite and cause an explosion when percentages above 40 percent oxygen are used.

Requirements for blends above EAN40

Whenever dive equipment comes into contact with a blend above EAN40, the equipment must be “oxygen cleaned.” Regulators, SPGs, cylinders and valves must either be purchased as "oxygen clean" or special cleaning procedures must be used to "oxygen clean" them. This can be an expensive and laborious task and must be performed by a trained professional regularly.

In addition, because the maximum operating depth is so shallow for blends above 40 percent, recreational divers will probably not be able to carry enough gas on the dive to realize any gain in the extended bottom times. For example, a dive to 50 feet with EAN36 gives you 220 minutes of bottom time! Chances are you will run out of air long before you ever reach the maximum time limit even on a repetitive dive with this blend.

So why do divers use higher blends?

Blends above 40 percent are generally used by technical divers in performing extended no decompression dives or to shorten decompression obligations on a decompression dive. This is a very different reason from using enriched air to extend bottom time. It is also very dangerous, since it requires the diver to switch gases during the dive.

You will learn these procedures in the PADI Tec 40 course, and they should not be attempted by an untrained diver. If you are interested in technical diving, get as much experience diving enriched air as possible before enrolling in a technical diving course. To learn more about technical diving, see our Technical Diving article.