Nitrox diving is a method of scuba diving steadily gaining popularity among divers who would like to dive for longer periods of time. The word "nitrox" is a portmanteau of the words nitrogen and oxygen, and can actually be used to mean a mix of the two gasses in any ratio. Since the air on the surface of the Earth is actually about 78% nitrogen and 21% oxygen (with 1% trace gasses), we can say that all land-based living things have breathed nitrox.

The basic difference between regular scuba diving and nitrox diving is in the way the air is mixed. Regular scuba has a very specific ratio of nitrogen to oxygen; it tries to mimic the air found on the surface of the Earth as closely as possible. Nitrox diving, on the other hand, tweaks this mixture to maximize bottom time, or time spent underwater, and minimize surface intervals. Surface intervals refer to the time required on the surface before one's next dive. While nitrox diving mixes come in a variety of ratios, they are usually classified into two types: hypoxic which are less than 21% oxygen, and hyperoxic which are more than 21% oxygen. Recreational and sport divers may only use hyperoxic nitrox mixes (also called "SafeAir," enriched air, "EAN" or EANx").

The underlying principle behind nitrox diving is relatively simple. As any experienced diver knows, the longer and deeper he goes underwater, the more nitrogen enters his system. Too much nitrogen in his system can lead to a slew of debilitating illnesses, some of which may ultimately result in death. To combat this, a diver must ascend slowly, make decompression stops, and observe the recommended surface interval before the next dive. For the recreational or sport nitrox diver, however, the plan is a little different. Since his "enriched" air has has more oxygen and less nitrogen (with the result that there is less nitrogen to enter his system), he may spend more time underwater, less time on decompression stops and surface intervals, and in some cases, may not need to make them at all!

However, this doesn't mean that nitrox diving is automatically safer than regular diving. One of the more important issues revolves around the fact that the interplay of gasses in our systems changes as the atmospheric pressure changes. This means that as a diver delves deeper in the underwater world, the gasses in his system begin to behave differently. While breathing even pure oxygen on the surface will probably not cause a person harm, oxygen toxicity, or oxygen poisoning, becomes more of a danger for nitrox divers. Also, diving with the wrong nitrox mix may actually increase a diver's vulnerability to complications, as certain ratios of nitrogen and oxygen do not work well at certain depths.

While nitrox diving has certainly been gaining a lot of followers, there is still quite a lot of confusion surrounding it. The problem lies in divers with improper or no training using nitrox without understanding the science involved. Some believe that nitrox diving will allow them to dive deeper, which is frankly not the case. In reality, the higher the percentage of oxygen in the nitrox mix, the shallower the maximum operating depth becomes. Most untrained divers also assume that nitrox diving will cause less narcosis and decompression sickness. While it is true that the risk of nitrogen narcosis may go down, one must remember that oxygen is also narcotic, and can pose a threat.

In such a highly technical sport such as nitrox diving, it is vital that one understands and adheres to the principles involved. After all, it could help save your life.