Wednesday, January 26, 2005
Nitrox diving. How and why
By: Scott Fraser
As a diver I’m sure you have heard of the term NITROX. Maybe your local dive shop was trying to push it as a specialty course, maybe you read about it in a scuba publication, or maybe you saw a NITROX sticker on a divers tank and thought, what in the hell is NITROX, Well I’ll tell you.
Basic air (what you breathe) consists of 79% nitrogen and 21% oxygen (O2). Basically NITROX increases the amount of oxygen in your breathing gas. If you get your scuba tank filled with a 36% NITROX mix you are now breathing 36% oxygen and 64% nitrogen.(Tanks are never to be filled with NITROX unless labeled NITROX ONLY, plus a NITROX course should be taken in order to educate yourself on the principles and physics of mixed gas diving) This NITROX babble is necessary why????, its not. Most divers are satisfied with diving simple air. Why the NITROX you ask, NITROX greatly extends your bottom time on a dive, also it decreases your no decompression limits (NDL). On the other hand it does put limits on the depth you can attain. It increases your bottom time by allowing your tissues to absorb less nitrogen by breathing a higher concentration of oxygen (O2), basically offsetting the horrible monster known as the bends. We all know about the bends, right?? Too much nitrogen absorbed can cause bubbles in your body’s tissues and blood stream. The effect is like that of a can of soda shaken violently and then suddenly opened. Without proper dispelling of the nitrogen it can form nitrogen bubbles in your body’s tissues and blood, turning your blood into foam. It can also cause nitrogen bubbles to become trapped in your joints causing severe pain. You curl into the fetal position and scream. The curling of elbows and knees into the fetal position is where the name the bends comes from. You bend inward. OUCH!!!!
When breathing a gas such as NITROX less nitrogen is absorbed allowing more bottom time on a dive and less, if any decompression. Also the deeper you go the more nitrogen your body absorbs, therefore breathing a higher concentration of oxygen (O2) you are absorbing less nitrogen therefore your bottom time is extended, making NITROX a good option for recreational scuba diving.
NITROX IS NOT A DEEP DIVING GAS. As I discussed before NITROX is an excellent alternative to air, staying within the recreational diving limits (0 ft- 130 ft). Let’s discuss a term that is horrible to divers: OXYGEN TOXICITY. Oxygen toxicity is caused by too much oxygen in your body. Yes, oxygen is a poison to the human body. Too much of anything can kill you right???? Moderation is the key to any human activity. Too much oxygen can block the needed flow of nitrogen to your blood. I know I spoke of nitrogen earlier as a deadly gas, but remember the air we breathe is made up of 79% nitrogen. So nitrogen being deadly at depth while diving, we still need it to survive. Too much oxygen consumed, blocking nitrogen, can cause a diver to take an (O2 oxygen hit). This is where the toxic amounts of absorbed oxygen cause a diver to become unconscious
and convulse uncontrollably. The diver takes a hit and passes out. Its not the oxygen that kills the diver, but the passing out causes the regulator to be spit from the divers mouth, causing a sudden intake of water into the lungs, resulting in drowning. It’s the excessive amount of oxygen absorbed that causes the diver to pass out. The diver looses consiousness which causes the regulator (breathing devise) to escape from his mouth. Without a regulator supplying your air you are sucking in water. When unconscious you aren’t aware of what’s going on, you begin to breathe water. YOU DROWN!!
I hate to bring up the ugly statistics of diving but I have to. Anything, when not used properly can be deadly. You have to learn to drive a car, hold a knife, start a fire, ETC. When used correctly, NITROX can be the best thing that ever happened to your scuba diving adventure.
Now on to the technical aspects of NITROX, Oh don’t worry, ill touch on the fun of NITROX as well. I just had to produce the facts before the fun. Its what I do (facts).
Although NITROX is not a deep diving gas (as before mentioned) it is a excellent decompression gas. When divers make descents to great depths (200 ft- beyond) They use a gas known as trimix. Trimix is a mixture of helium, oxygen, and nitrogen. I will not get into the explanation of trimix diving. That’s another article on its own. The decompression methods used by deep trimix divers requires off gassing of nitrogen just like recreational diving. Deep divers use stage bottles which contain gasses to decompress on, the reason they do this is to release nitrogen bubbles from the blood stream. The most popular decompression gas is NITROX. These dives carry a bottle of NITROX On there ascent from the deep they stop at certain depths to allow nitrogen to be released from their tissues and blood stream. To help the off gassing they switch tanks and breathe a NITROX mixture. This high concentration of oxygen, inhaled, allows the diver to surface faster, allowing nitrogen to leave the blood stream, avoiding the BENDS. The diver breathes the oxygen enriched air (NITROX), pushing nitrogen from the blood allowing a safe return to the surface. I will get into decompression theory and trimix diving in a later issue. These are just some of the realities associated with NITROX diving, or should I say “technical diving. These procedures are not applied to recreational (no decompression diving). A recreational NITROX diving certification does not include decompression of any magnitude. I’m just giving you the facts of all aspects of NITROX!!
NITROX for a recreational diver means: longer bottom time, less of a fatigued feeling at the end of a dive, no decompression on a dive that air requires, less chance of decompression sickness (the bends). Here are some examples from recreational dive tables comparing air to NITROX as far as bottom time and length of a dive (you paid for the dive, might as well stay under as long as you can).
If you love to dive and would like to make your experience last longer, consider NITROX diving. Its good for recreational diving, it is a must in technical diving and it becoming more common place in the diving community all together. Contact your local dive shop or CFPSI (below) and find out about a NITROX certification. IT COULD SAVE YOUR DIVE!!
I'm still reading through all your posts, but I thought I'd start at the bottom and work my way up.
The benefits of NITROX for the sport diver I believe really lies in "less of a fatigued feeling at the end of a dive, no decompression on a dive that air requires, less chance of decompression sickness (the bends)" IF you execute exactly the same air dive on NITROX. Obviously if you use NITROX to extend your bottom time and you then push your no-decompression limits then you've gained bottom-time, but you then experience a little less of the other benefits.
I'll definitely add to my blog in terms of what diving in Southern Africa entails, and will keep a keen eye on your blog because Florida is very well known for it's cave diving. Happy diving.