Enriched Air Diving

By Ric Abbott

There are many misconceptions around enriched air diving. This dive article will provide some facts about enriched air, advantages and disadvantages of diving with enriched air, and equipment used for enriched air diving.


Air is a mixture of primarily two gases, approximately 21% oxygen and 79% nitrogen. Nitrogen is the culprit in causing decompression sickness, more commonly know as the "bends". This fact will be important as we discuss enriched air advantages. Enriched air is the result of adding oxygen to air, raising the level of oxygen in the mixture to between 22% and 99%. However, for recreational purposes enriched air blends range from 22% to 40% oxygen. Nitrox is often referred to as "enriched air"; however there is a difference between the two. Nitrox refers to any nitrogen-oxygen mixture, while enriched air is air that has some oxygen added. Therefore by definition enriched air can only contain greater than 21% oxygen. The two most common blends are 32% oxygen (EANx32) and 36% (EANx36). The abbreviation EAN stands for Enriched Air Nitrox.

The primary advantage of enriched air is to extend the no stop limits beyond the normal no stop limits associated with air. Since enriched air has a lower level of nitrogen than air, you absorb less nitrogen while your body is able to metabolize the extra oxygen, assuming you are diving within recreational enriched air limits. This results in longer no decompression limits while diving on enriched air. The primary disadvantage of diving with enriched air is potential exposure to oxygen toxicity. Oxygen can be toxic based on depth and duration under water, and by increasing the level of oxygen in the gas you breathe, you are constrained by your depth and duration. This is why you must calculate both your no decompression limit due to nitrogen, and your oxygen exposure limit called partial pressure. For most non-repetitive dives under 100 feet, you will be limited by the amount of gas as opposed to either the no decompression limit or the partial pressure limits. Enriched air is particularly effective in enhancing the frequency and duration of repetitive dives, since nitrogen buildup is lessened.

Enriched air diving within the recreational limit of under 40% oxygen requires some special equipment, but for the most part you can use the equipment you purchased for diving air. The only new piece of equipment that you will definitely need is a tank. One reason for this is the special markings that must go on an enriched air tank; the other is that the tank must be cleaned and lubricated for oxygen exposure to facilitate partial pressure blending which involves adding pure oxygen to air. A common scuba community guideline is that regulators, BCDs, SPGs and alternate air sources may be used with enriched air blends up to 40% oxygen without modification. However, you should verify that the manufacturer of each piece of equipment has certified that equipment for use with enriched air. For gas mixes with more then 40% oxygen, special equipment is required. As with any scuba equipment, regular servicing is highly recommended, including O-rings and other critical components. During your enriched air training, you will learn how to properly fill and verify the blend of gas in your tank. The verification step is extremely important and must be done by you the diver; you shouldn't rely on anyone else to verify your gas blend.

Remember, you should never dive with enriched air unless you have been certified by a reputable certification organization. While the benefits of diving enriched air are significant, so are the risks.

Rick Abbott is an avid diver, part time author, and consultant in the IT field. For more dive articles and tips, go to http://www.divervillage.com If you are a writer and like writing articles about diving, submit your articles to http://www.divervillage.com where divers can read them online. Also, visit's Rick's diving blog at http://divervillage.blogspot.com

Too Old To Learn Scuba Diving?

By Rona Limsy

We are always told we should learn sports when we are young, when our bodies are more resilient to the bruises and bumps which can be afflicted on us when we learn a new sport. This is true to a certain extent.


Take for example, my experience learning wind surfing. I learnt the sport when I was 26. If I were to learn this sport now at age 42, chances are I would not go far and would probably give up after 1 or 2 tries. Learning wind surfing was like battling with all the forces at the same time! We're talking about trying to balance on choppy waves on a slippery wet board, at the same time maneuvering a sail which weighs more than you in the correct direction that you want to go.In the process, I contributed blood and flesh from cuts on barnacles and bruises from hitting the surf board more than once before falling into the waters.

But there is a huge difference with scuba diving. YOU ARE NEVER TOO OLD TO LEARN SCUBA DIVING. I can never say this enough. I learnt scuba diving when I was 38. Now I'm not saying that 38 is a ripe old age but still, the body does feel somewhat less strong and less resilient. Added to that, as we get older, we also seem to have more fears. Perhaps we feel we have more to lose if something should happen to us.

I say middle age and beyond should never be a factor in learning scuba diving BUT you do need to have these:

1) an intense love for the sea 2) a willingness to learn from someone younger than you 3) relatively good health and lastly but very important 4) time and money

Now I'm assuming that you are thinking of learning scuba diving because you want to make this a sport that you can enjoy every other weekend if time and money permits and not just learning for education's sake.

An Intense Love for the Sea To enjoy a scuba diving trip, you will have to love the sea and I mean really really love it with all its wonderful creatures large and small. You will know what I mean on your first ever scuba diving trip after you have cleared your Open Water tests.

It is unlikely that your scuba diving buddies on your first dive trip will be the same classmates in your scuba diving course. Because of time and money constraints, you will find that you may be the only one keen enough to join a scuba diving trip soon after your certification.

More often than not, your dive buddies will be a dive-crazy bunch who will do at least 4 dives a day plus another at night. This means that on a scuba diving trip, most times you will not do anything but dive, talk about the sea creatures and encounters of each dive, before suiting up for the next dive. For someone who only wants to do one dive a day and then go shopping, he/she may be disappointed as many great scuba diving spots have few of these shopping and entertainment facilities.

In case you are already getting stressed just thinking about this, don't be. Every scuba diving newbie goes through this. Just have an attitude of a newbie, be humble and you will find that the seasoned divers are more than willing to share tips and may even help you to gear up before a dive.

A Willingness to Learn from Someone Younger than You Your scuba diving instructor is likely to be someone much younger than you. Some dive instructors have an attitude and are cocky so you may have to live with it for at least 3 weekends before you become certified - 1st weekend for classroom and theory, 2nd weekend for pool sessions and a 3rd weekend for the actual open water tests. Put aside your ego and just bear with it, it'll be worth it in the end.

Having said that, that's not to say that there are no good and kind scuba diving instructors around. I was fortunate to receive dive instruction from PC, a very kind and patient man, without whom my dive learning experience would not be as smooth and enjoyable.

Relatively Good Health It's not necessary to be in peak fitness before you can take up scuba diving. However, you would need some strength to be able to walk with full scuba diving gear strapped on you. Once you enter the waters with all your gear, you are almost weightless. But it's the few steps you have to make to get into the boat or to cross the beach into the water that may be a challenge for a person who is not used to carrying heavy loads on them.

Having said that, some scuba diving resorts have fantastic dive staff who can help to overcome this by carrying the tanks and gear to the boat for you to suit up inside the boat. And of course if you are on a live-a-board (live, eat, dive, sleep, on board a boat throughout the dive trip), then this may not be relevant.

Time and Money This is probably the 2 most deciding factors of whether someone continues to enjoy scuba diving after passing the Open Water tests. Getting certified through a scuba diving course is very fast, just 3 weekends basically. And not too expensive, probably about $300 to $400, including an out-of-the country dive trip for the open water tests. But unless you live near a scuba diving area, you are most likely going to have to travel a distance or even out of the country to do a good dive.

Now just think how much each trip is going to cost you and multiply that by how many times you would love to do scuba diving in a year. When you do the sums, it can be staggering. So you cut down the number of dives you want to do in a year, and then calculate and cut down some more.

In our scuba diving class, my husband and I were the only ones who continued to dive after the class was over. Even then, we did not manage to do the number of dives we would really have loved to do in a year. That's how it finally ends up that we are doing an average of 1 dive a year. This more or less ensures that we will always be diving as a "scuba diving newbie" (hence the blog's name). A scuba diver gets "rusty" when the interval is too long between each dive trip. Ideally, we should dive at least once each quarter.

I have not even gone on to calculate the other "investments" to personalise your gear such as your own BC (buoyancy control), your own octopus (breathing appartus) and your wet suit.

Having said all this, I still believe it's never too old to learn and enjoy scuba diving. Even with our limited dives since we were certified and diving as scuba diving newbies, we enjoy each and every one of our dive trips. Find the right people to dive with, find a fantastic dive spot that suits your preferences (whether macro, to check out small sea creatures, or see bigger fish) and nearby spa facilities to sooth your body aches after a dive - it's a wonderful combination that will almost always ensure a great scuba diving experience!

A scuba diving newbie can still enjoy happy diving!