Before you enroll in this course, you should purchase or rent a programmable Nitrox computer. Almost every manufacturer today offers Nitrox dive computers at prices that put them well within the budget of the majority of active divers. You may also find that many SDI dive centers and resorts rent Nitrox programmable computers.
Renting a Nitrox computer may be an excellent way to check out a specific model before buying, but be careful that you fully understand how your rented computer works before diving with it. If you rent a computer from a dive center, be sure to ask them to provide you with a copy of the manual, or at the very least, have them explain the computer’s functions to you so that you fully understand them.
Most dedicated Nitrox computers simultaneously track and display your nitrogen absorption for decompression calculations, as well as monitoring your oxygen exposure. If you are making multiple deep dives in a single day, this type of information is extremely important.
Some of the more sophisticated models even allow you to change gas mixtures while diving, a feature used by many technical divers, who switch to mixtures containing higher percentages of oxygen for decompression.
Most modern Nitrox dive computers allow you to set the percentage of oxygen in your breathing mix anywhere between 21 percent and 50 percent oxygen. A few will even allow richer mixtures. However, most require that the percentage of oxygen in the mixture be set before you enter the water. This procedure must be done prior to the start of every dive.
Some Nitrox dive computers will default to 21 percent oxygen (air) when they are first “booted up” at the start of a dive day. Others will retain whatever mixture at which you set them. Whatever type of computer you use, it is essential that you verify that it is properly set for the mixture you wish to use before each dive. This is essential for the computer to calculate your decompression and oxygen exposure properly.
In most other ways, Nitrox dive computers do not differ from air diving computers. They provide the same type of dive planning, repetitive dive calculations, and log functions.
In addition to programming your computer with the information on the mixture you will be using, you will also need to program it with the maximum partial pressure to which you are willing to expose yourself. To get the maximum depth capability from EAN32, you need to program your computer for a partial pressure of oxygen of 1.6. If you want to be more conservative, you can set your dive computer for a PO2 of 1.5 or 1.4.
It’s important to remember that none of the dive computers currently available provide an exact measurement of the nitrogen and oxygen levels inside your body. The computer only shows a mathematical model of what diving physiologists think is going on. Even if you follow your dive computer exactly, it’s still possible to experience decompression sickness or oxygen toxicity. However, these same risks apply to using dive tables, with the added risk that it is far more likely that a diver will make mistakes in his calculations when using tables and formulas.
You may also see divers using air diving computers with Nitrox. This is far from an ideal situation, as not only does one lose the advantage of the additional bottom time provided by using enriched air, air computers do not track one’s exposure to oxygen, and this must be done manually.
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