NAUI Scuba Diver 126 DIVE LIMITS DEPTH NAUI LIMIT U.S.N. LIMIT 0-20’ (0-6m) No Limit No Limit 21-40’ (6.4-12m) 130 mins. 200 mins. 41-50’ (12.5-15m) 80 mins. 100 mins. 51-60’ (15.5-18m) 55 mins. 60 mins. 61-70’ (18.6-21m) 45 mins. 50 mins. 71-80’ (21.6-24m) 35 mins. 40 mins. 81-90’ (25-27m) 25 mins. 30 mins. 91-100’ (27.6-30m) 22 mins. 25 mins. lessens the risk. Divers who use time limits in excess of the recommended limits (for example, technical divers) recognize and accept the increased risk that is associated with these longer dive times and the need for special decompression procedures. Deeper diving requires experience, planning, and training. As a certified entry-level NAUI Scuba Diver, you should not dive to depths deeper than 18 meters (60 feet). As a certified NAUI Advanced Scuba Diver, you should not dive to depths deeper than 30 meters (100 feet). The maximum recommended depth for all recreational divers is 40 meters (130 feet). You do not need to memorize the dive time limits. They are included in your NAUI Dive Tables or your NAUI Dive Time Calculator. Note that the dive time decreases as the depth increases. If you are using a dive computer, the limits will probably be different from the limits presented in this textbook. Nitrogen offgassing occurs at different rates among your various body tissues. The rate of offgassing for different tissues is the basis for the non-linear variation in time limits for different depths. You should be familiar with this concept because it does form the basis for the calculations performed by dive computers and the time limits established by dive tables and dive computers. When you take the NAUI Master Scuba Diver course, you will learn various principles and theories behind dive tables. Residual Nitrogen To properly use dive tables, dive time calculators, and dive computers, you must understand the concept DEPTH DIVE #2 TIME DIVE #1 of residual nitrogen. In reality, it takes hours to fully absorb nitrogen into your body or fully eliminate nitrogen from your body. If you dive and absorb nitrogen at depth, ascend to the surface, and then make another dive within 24 hours of the first dive, you will still have nitrogen in your body from the first dive (figure 5-3).This is called residual nitrogen. Your body will absorb nitrogen from the second dive in addition to the nitrogen remaining from the first dive. You must always take the nitrogen remaining in your system from any previous series of dives into account when planning your next dive. This residual nitrogen reduces your time limits for any given depth on your next dive. Verify What You Have Learned Review the following questions about ingassing and outgassing nitrogen: 1. When you go under pressure, your body ______________ nitrogen until it reaches a state of ____________________. 2. Bubbles form during offgassing when you ___________________________. 3. You can dive to ______ meters (______ feet) without a dive time limit. 4. Residual nitrogen is the nitrogen ___________________________. Decompression, Dive Tables, and Dive Computers FIGURE 5-2. RECREATIONAL DIVING USES SHORTER DIVE TIME LIMITS THAN THE US NAVY TABLES. Represents Residual Nitrogen DIVE #3 FIGURE 5-3. RESIDUAL NITROGEN IS THE NITROGEN THAT STAYS IN YOUR BODY FROM DIVES MADE IN THE PREVIOUS 24 HOURS.
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