NAUI Master Scuba Diver 172 Decompression and Recompression PROCEDURAL CHANGE RULE 1. Weight belt adjustment (sw to fw) Remove 2 1/2% of total weight of diver and ocean gear from weight belt 1.5 kg to 4 kg (3 to 10 lbs). 2. Flying after an ocean dive Wait 24 hours before flying following dives that do not exceed time limits and even longer following any dive situation (even though you have not made a dive) when you first reach any higher altitude dive site. This circumstance will require you to assume that you are in a higher group letter depending on the altitude to which you have arrived. This is due to relative nitrogen accumulation (excess nitrogen) in your body due to the altitude (and partial pressure of nitrogen) change, which will require several hours to normalize (table 5-6). 3. You should never use unmodified standard sea-level dive tables (e.g. NAUI, U.S. Navy, or others) when diving at altitude. Further, you must have the dives requiring decompression. 3. Diving on same day as Treat as a repetitive dive. Adopt repetitive dive group letter G on arrival for elevations up to arrival at altitude 10,000 feet. 4. Decompression • If dive is not too deep, use capillary depth gauge readings directly with the U.S. Navy Dive Tables to determine allowable bottom time. Use readings directly for 9m/min(50 ft/min) ascent rate and depths of any decompression stops. • If dive is deep or if capillary gauge is not available, use any other depth gauge and: — determine equivalent ocean depth, ascent rate and depth of any decompression stops from the altitude dive tables. — apply the equivalent ocean depth to the U.S. Navy Dive Tables to obtain allowable bottom time, and decompress accordingly. 5. Depth gauge correction • For capillary gauges, if above 3,000 feet, subtract 3% of reading per 1,000 feet of elevation. TABLE 5-4. SUMMARY OF PROCEDURES FOR DIVING AT ALTITUDE Altitude Pressure meters ATM PSI Bar kg/cm^2 mm Hg in Hg 0 1.0 14.70 1.013 1.033 760.0 29.92 300 0.963 14.16 0.976 0.995 732.0 28.82 600 0.928 13.63 0.940 0.959 705.1 27.76 900 0.894 13.13 0.905 0.923 679.1 26.74 1200 0.861 12.65 0.872 0.889 654.1 25.75 1500 0.829 12.18 0.840 0.857 630.1 24.81 1800 0.799 11.73 0.809 0.825 606.9 23.89 2100 0.769 11.30 0.779 0.795 584.5 23.01 2400 0.741 10.89 0.751 0.765 563.0 22.17 2700 0.714 10.49 0.723 0.737 542.3 21.35 3000 0.687 10.10 0.696 0.710 522.3 20.56 3300 0.662 9.73 0.671 0.684 503.1 19.81 3600 0.638 9.37 0.646 0.659 484.6 19.08 3900 0.614 9.03 0.622 0.635 466.8 18.38 4200 0.592 8.69 0.599 0.611 449.6 17.70 4500 0.570 8.37 0.577 0.589 433.0 17.05 TABLE 5-5A. ATMOSPHERIC PRESSURE VS. ALTITUDE (METRIC) Altitude Pressure feet ATM PSI Bar kg/cm^2 mm Hg in Hg 0 1.0 14.70 1.013 1.033 760.0 29.92 1000 0.963 14.15 0.975 0.995 731.6 28.80 2000 0.927 13.62 0.939 0.957 704.2 27.73 3000 0.892 13.11 0.904 0.922 677.9 26.69 4000 0.859 12.62 0.870 0.887 652.6 25.69 5000 0.827 12.15 0.837 0.854 628.2 24.73 6000 0.796 11.69 0.806 0.822 604.7 23.81 7000 0.766 11.26 0.776 0.791 582.1 22.92 8000 0.737 10.83 0.747 0.762 560.3 22.06 9000 0.710 10.43 0.719 0.733 539.4 21.24 10000 0.683 10.04 0.692 0.706 519.2 20.44 11000 0.658 9.66 0.666 0.679 499.8 19.68 12000 0.633 9.30 0.641 0.654 481.1 18.94 13000 0.609 8.96 0.617 0.630 463.1 18.23 14000 0.587 8.62 0.594 0.606 445.8 17.55 15000 0.565 8.30 0.572 0.583 429.2 16.90 TABLE 5-5B. ATMOSPHERIC PRESSURE VS ALTITUDE (IMPERIAL) CONVERSION FACTORS: ATM = EXP (-0.0381 * ELEVATION / 1000 FEET OR 304.8 M ) PSI = ATM * 14.69595 BAR = ATM * 1.01325 KG/CM^2 = ATM * 1.033227 MM HG = ATM * 760 IN HG = ATM * 29.92126
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