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Flying after Diving If you decrease pressure below one ATM by going to an altitude above sea level after diving, you increase your risk of suffering DCS. Commercial planes pressurize their cabins to an altitude equivalent to about 2400 meters (8000 feet) or 0.75 ATM or less. If you only do one no-decompression dive, you can fly after waiting 12 hours. If you do more than one no-decompression dive in a day, or do multiple days of diving, you should wait longer. The current recommendation is to wait 24 hours after the completion of your last dive. If you make dives that require a decompression stop, or you omit a required decompression stop, wait more than 24 hours before flying. Altitude Diving Atmospheric pressure decreases with altitude, which means that the rate of change in pressure is greater when you descend into water at altitude. To account for this difference, you need to use altitude conversion tables or the NAUI Altitude Tables and follow special procedures. Before you dive at altitudes above 300 meters (1000 feet), you must be trained in special altitude diving procedures. Your table depths, maximum rate of ascent, and the depths for decompression stops change with altitude. Your depth gauge will also give incorrect data. If altitude diving is common in your area, your instructor might provide additional information as part of your course, and also might recommend that you participate in a high-altitude specialty-training program before you receive your NAUI Scuba Diver certification. High-altitude training is beyond the scope of this textbook. Do not attempt high-altitude diving without first completing an appropriate high-altitude training program. USING THE NAUI DIVE TIME CALCULATOR The NAUI Dive Tables are the basis for the NAUI Dive Time Calculator, which eliminates some calculations required with the tables (figure 5-18). Once you are familiar with the NAUI Dive Tables, learning how to Chapter 5- Decompression, Dive Tables, and Dive Computers use the NAUI Dive Time Calculator is easy. General Organization NAUI Dive Tables 1 and 3 are combined on the baseplate. Letter Group designations appear around the circumference, and ADTs in minutes appear in the window. End-of-Dive Letter Groups appear to the right of the ADT numbers in the disk window. Dive Table 2 is printed on the disk. Using the Calculator To plan your first dive of the day, use the following steps: 1. Find the No Group section on the baseplate. 2. Align the depth arrow on the edge of the disk with the planned depth of your dive. The Maximum Dive Time for that dive appears as the largest number in the window. For example, a No Group diver who plans a dive to 18 meters (60 feet) would have a Maximum Dive Time of 55 minutes. To find your Letter Group at the completion of your dive, use the following steps: 1. Find the No Group section on the baseplate. 2. Align the depth arrow on the edge of the disk with the deepest depth of your dive. 3. Read the bottom times from the center of the disk outward and find the first time that you do not exceed. 4. Look to the right of the window to see your End- Of-Dive Letter Group. For example, if you do a dive to 18 meters (60 feet) and your ADT is 23 minutes, the first time you do not exceed is 25 minutes. The End-Of-Dive Letter Group next to the 25 is E. To plan a repetitive dive, use the following steps: 1. Use Dive Table 2 on the disk to find your new Letter Group after your SIT. 2. Find your new Letter Group on the circumference of the baseplate and align the depth arrow on the disk with the planned depth of your repetitive dive. For example, if you have a Letter Group of Decompression, Dive Tables, and Dive Computers 139


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