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If you are already a certified diver you have probably heard of the terms Nitrox or Enriched Air diving but like many people, may have associated diving with these gas mixtures as the domain of Technical or commercial divers only. Although Technical and commercial divers do commonly use nitrox blends of breathing gas, Enriched Air Diving has become very popular, safe and now readily available option for recreational divers.

But first before I dive into some of the benefits and potential hazards of Enriched Air diving lets start with the basics of what a diver is breathing with a normal air fill in his tank and the differences when it’s Enriched Air. The air we are all breathing now consists primarily of two gases: nitrogen (79%) and oxygen (21%). There are very small quantities of other trace gases in the air we breathe but for practical purposes we can ignore them here. This same 79% nitrogen and 21% oxygen air is usually what we divers have in their scuba tanks, although it has been compressed and has much of the moisture removed during the filling process of the tank.

This standard air fill has been used by recreational divers all over the world since the conception of sport diving, but as all divers know there are limits to how long one can spend underwater at depth. These limits are governed by our body’s absorption of nitrogen at depth and are commonly known as our “No Decompression Limits”.

Simply put recreational no decompression diving allows us through the use of dive tables to monitor the amount of nitrogen our body absorbs on any dive. As long as we stay within these depth and time limits we can ascend directly to the surface without the need for lengthy decompression stops on the way to the surface.

But with anything as captivating as cruising the beautiful underwater habitat there is always that yearning to stay longer. Developments in equipment such as larger or higher pressure dive cylinders and multilevel dive tables or dive computers have given the diver the opportunity of remaining longer at depth.

Well Enriched Air is simply another tool or option to allow divers to extend their dive time and enjoyment within the 15 – 30 meter depth range. Enriched air replaces some of the nitrogen you breathe underwater with oxygen, so that during a dive you absorb less nitrogen than you would breathe normal air. Your body metabolizes and otherwise absorbs the extra oxygen, so that within the limits of recreational enriched air diving it does not contribute to bubble formation after the dive. This allows you longer no decompression limits for each depth, how much longer depends on the enriched air blend you are using for that dive. For example if you use the PADI RDP (recreational dive planner) to calculate your maximum time at 18 meters on normal air you will find that you’re no decompression limit to be 56 minutes. But using a 32% (oxygen) Enriched air mix the PADI Enriched air table will allow you a 95 minute NDL and with a 36% mix that no decompression limit goes up to 125 minutes !

As with everything in life you can not get something for nothing, as you reduce your nitrogen exposure you increase your oxygen exposure and oxygen does have its own very hazardous set of problems at depths! Without going into great detail, when you increase you oxygen percentage in the gas mix you decrease the depth at which you can safely breathe that mixture. The danger of exceeding safe depth limits of enriched air has possible consequences that are both more hazardous and more immediate that diving with air.

Now to become certified as a PADI Enriched Air diver is a one day course in which you will learn all you need to know about diving safely with Enriched air mixtures from 22 – 40%. The course covers the advantages and disadvantages of diving with enriched air, equipment considerations, managing oxygen exposure and using the Enriched air dive tables. You will then undertake two enriched air dives with your PADI instructor with the emphasis on pre-dive planning and adhering to the time and depth limits called for by enriched air procedures.

Enriched air diving may not be for everyone and most certainly not for every dive; you’ll probably find that you still use air for some of your diving activities. Most times when conducting multilevel dives using a dive computer you will find it is the amount of gas in your tank that dictates how long you may spend underwater not the no-decompression limits. Some dives enriched air may be very advantageous and others unimportant. Personally I have found enriched air a great advantage when staying for long periods at one depth to get that special picture of an elusive marine critter. Enriched air is another tool you can have as a diver to allow you to safely extend your bottom time and get the most out of my dives.

 Check out which Dives Centers offer Enriched Air training and facilities in your area at www.dive-directory.com

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