Once upon a time, there came a magical gas that promised deeper, longer dives. Some people flocked to this mystical world, regaling their friends with tales of increased energy and a weapon with which to battle the evil monster known as Decompression Sickness. Others were reluctant, mistrustful of the new technology, and they stayed within their regular air realms.
But that was a long time ago in a galaxy not so far away, before mixed diving gases started becoming more en vogue. Nitrox has been part of recreational diving for more than two decades and has made room for Trimix, which adds helium to the nitrogen/oxygen combo. So what are the pros and cons of using mixed gases, and which circumstances would better lend themselves to plain old air?
Nitrox contains an average of 32-36 percent oxygen (versus the usual 21 percent), and has long been purported to give you longer bottom time. Many divers also feel more energized after a nitrox dive. Science has yet to be able to pinpoint why this is, but many folks make the claim nonetheless. Nitrox also decreases your surface intervals, meaning you can get back in the water quicker. Seems great, right? Who wouldn’t want to spend more time at the bottom?
Nitrox does extend your dive but not perfectly. You’ll have to do some math in order to get the most out of your mix. For example, using 32 percent at 70 feet extends the recommended 50 minute dive time by about 10 minutes. Using a 40 percent mixture at the same depth can double your time to 100 minutes. And, like the reduction in fatigue that many users report, there is no hard evidence that it makes you bullet proof against narcosis, so be wary.
One advantage regular air has over nitrox is that you are better off using your regular 21 percent mixture if you’re going below 120 feet. A 36 percent or higher mix is actually more dangerous at depth and can lead to oxygen toxicity. Another is that nitrox users require additional training. If you are an occasional recreational diver, you may want to carefully weigh the pros and cons before making this extra investment.
So, regular air divers have depth limits and shorter bottom times. Nitrox users risk OD’ing on O2 when they go deeper than 120 feet. For a growing number of advanced divers, Trimix is the solution to these problems. This blend of oxygen, nitrogen, and helium is definitely not for the “once in a while” diver. The mix can be custom blended to suit a particular environment, but requires additional gear and training. It is also more costly at the fill station. But if you regularly dive deep, this could be well worth it.
Bottom line, with the proper training and equipment, you can customize your mix to fit your dive and get the most out of your scuba certifications.