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Chapter 5- Decompression and Recompression Decompression and Recompression 173 feet meters * Letter Group 1000 305 B 2000 610 B 3000 915 C 4000 1220 D 5000 1525 D 6000 1830 E 7000 2135 E 8000 2440 F 9000 2745 F 10000 3050 G 11000 3355 G 12000 3660 G 13000 3965 H 14000 4270 H 15000 4575 I * approximate conversions from feet to meters TABLE 5-6. REPETITIVE DIVE GROUP ON ARRIVAL AT ALTITUDE FROM SEA LEVEL. information to correctly modify usage of the tables so that you can correctly determine your allowable bottom time and ascent rate for the altitude at which you dive. All standard tables are based on “sea water at sea level” calculations, and your altitude dive(s) are vastly different from the conditions on which the standard dive tables were based. The following information must be obtained in order to use dive tables at higher altitudes: • The equivalent ocean depth of your dive. • The allowable ascent rate of your dive (table 5-7). • The depth of any (potential) decompression stops you may need to make. A capillary depth gauge can be used on shallow to medium depth dives. At altitude, capillary depth gauge readings are actually greater than the true depth and can be used without correction to determine your allowable bottom time and decompression stops. As an example, at any altitude the capillary depth gauge reading of 12 m (40 ft) may be interpreted as 12 m (40 ft) on no-decompression time available on the first dive. Further, you may then read the gauge directly for any indicated decompression stops; i.e., if a 3 m (10 ft) stop is required, you may stop at the capillary depth gauge reading of 3 m (10 ft) to accomplish the necessary stop. Altitude / Elevation Ascent Rate Meters mfw per minute 0 9.3 300 8.9 600 8.6 900 8.3 1200 8.0 1500 7.7 1800 7.4 2100 7.1 2400 6.9 2700 6.6 3000 6.4 3300 6.1 3600 5.9 3900 5.7 4200 5.5 Altitude Rate = Sea Level Rate * EXP (-0.0381 * Elevation/304.8 m ) TABLE 5-7A. MODIFIED FRESH WATER ASCENT RATES EQUIVALENT TO AN OCEAN RATE OF 9M/MIN. Altitude / Elevation Ascent Rate Feet ffw per minute 0 30.9 1000 29.8 2000 28.6 3000 27.6 4000 26.5 5000 25.5 6000 24.6 7000 23.7 8000 22.8 9000 21.9 10000 21.1 11000 20.3 12000 19.6 13000 18.8 14000 18.1 Altitude Rate = Sea Level Rate * EXP (-0.0381 * Elevation / 1000 feet ) TABLE 5-7B. MODIFIED FRESH WATER ASCENT RATES EQUIVALENT TO AN OCEAN RATE OF 30 FT/MIN.


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