How to Dive With Nitrox
- 1). Get nitrox certified. Technically, nitrox refers to any gas mix that's primarily made up of nitrogen and oxygen, but most people use the term interchangeably with the more correct "enriched air nitrox," which indicates an oxygen percentage is above the norm of about 21 percent. Dive shops and boats require that divers using nitrox gas be certified to do so. This is because, while nitrox lowers some risks, it raises others. Because nitrox contains a smaller percentage of nitrogen than regular air, the risk of decompression-related illness is reduced and the amount of time that can be spent at depth is increased. But the larger concentration of oxygen puts the diver at risk for oxygen toxicity. An understanding of the limitations nitrox presents is essential. Luckily, it's easy to find a certification course. Besides regular dive shop classes, courses can be found online, and some dive operations even offer nitrox courses on the boat.
- 2). Get a nitrox fill. You'll need to show your nitrox certification card to do so. If the shop makes nitrox by partially filling the tank with regular air and then adding 100 percent oxygen, the tank must be "O2 clean." If the shop has a bank or membrane system, they are able to premix the gas before it goes into your cylinder. Since they're never pumping 100 percent oxygen into the tank, it's not necessary that the tank be specially cleaned for oxygen. In this case, though, you'll want to bring the tank in with only a small amount of air so the nitrox percentage will be higher.
- 3). Analyze your gas mix. If you're diving nitrox regularly, you'll want to invest in an O2 analyzer of your own. Otherwise, use the analyzer provided by the shop or dive boat. Regular air contains approximately 21 percent nitrogen; nitrox typically aims for a 32 percent mix, but the percentage will be unique and depends on both the fill system and the pre-fill contents of your cylinder. It's important you know the percentage that's in your tank, because different gas mixes have different maximum depths, and failure to pay attention to this can have dire consequences. Most shops or boats will require that you log your percentage to indicate you tested it personally, and that you understand the maximum depth of the mixture you're breathing. Don't rely on the shop or boat for this information.
- 4). Set your dive computer to the proper percentage. This will allow it to calculate your no-decompression limit (NDL) and maximum depth accurately. If you're doing multiple dives, make sure to analyze the gas every time you get a fill, and adjust the computer accordingly. Note that many computers reset to regular air, a 50 percent mix or even to 100 percent oxygen at midnight on a given dive day. Care must be taken to confirm that your computer is set to the right mixture.
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