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Chapter 5- Decompression, Dive Tables, and Dive Computers Decompression, Dive Tables, and Dive Computers 131 number in the block is the minimum Surface Interval Time (SIT) for a particular group and the upper number is maximum SIT for a particular group. To find your new Letter Group based on your SIT, use the following steps: 1. Look across the top row of the table until you come to the Letter Group designation you had at the end of your previous dive. For example, you had a Letter Group of G. 2. Go down the column until you find the block into which your SIT fits. For example, you were out of the water for three hours. The block into which three hours fits is the one which starts at 2:59 and ends at 4:25. 3. Move left across the row containing your corresponding block until you come to another letter. For example, if you had a Letter Group of G and were out of the water for three hours, you would have a new Letter Group of C. Note that the maximum time in this table is 24 hours. All excess nitrogen is considered eliminated after you have been on the surface for 24 hours. Therefore, a dive after 24 hours on the surface is not considered a repetitive dive. Verify What You Have Learned Review the following questions about Table 2: 12. If you have a Letter Group of I and your SIT is 2 hours and 36 minutes, your new Letter Group is ____. 13. If you have a Letter Group of C and your SIT is 3 hours, your new Letter Group is ____. 14. If you have a Letter Group of G and your SIT is 42 minutes, your new Letter Group is ____. Table 3 - Repetitive Dive Timetable Table 3 – Repetitive Dive Timetable provides your Adjusted Maximum Dive Time (AMDT) for your next dive and your Residual Nitrogen Time (RNT) based on your current Letter Group (figure 5-10). You use this table twice for each repetitive dive. First, you use the table to find your AMDT when planning your dive. Next, you use the table to find your RNT after you complete your dive. You add the RNT to your Actual Dive Time (ADT) to find your Total Nitrogen Time (TNT). The table is arranged with the depths from 12 5-10 Converted meters to 40 meters (40 feet to 130 feet) in columns across the table and the Letter Groups in rows down the table. Each block of the table contains two numbers. The upper number is the RNT corresponding to each depth and Letter Group. The lower, red number is the AMDT for each depth and Letter Group. Use the following steps to find your AMDT when planning a repetitive dive: 1. Find your new Letter Group, based on your SIT, in the column on the right side of the table. For example, you have a new Letter Group of C. 2. Search along the row corresponding to your Letter Group until you come to the column corresponding to the depth to which you want to dive. For example, you want to dive to 15 meters (50 feet). 3. Look at the lower number to find your AMDT. For example, with a Letter Group of C, you can dive to 15 meters (50 feet) for a maximum of 59 minutes. A B C D E F G H I J K L 24:00 9:13 9:12 6:03 6:02 4:36 4:35 3:37 3:36 2:54 2:53 2:20 2:19 1:50 1:49 1:26 1:25 1:05 1:04 0:46 0:45 0:27 0:26 0:10 24:00 8:59 8:58 5:49 5:48 4:20 4:19 3:22 3:21 2:39 2:38 2:04 2:03 1:36 1:35 1:12 1:11 0:50 0:49 0:29 0:28 0:10 24:00 8:51 8:50 5:41 5:40 4:03 4:02 3:05 3:04 2:21 2:20 1:48 1:47 1:20 1:19 0:55 0:54 0:32 0:31 0:10 24:00 8:22 8:21 5:13 5:12 3:44 3:43 2:45 2:44 2:03 2:02 1:30 1:29 1:00 0:59 0:34 0:33 0:10 24:00 8:00 7:59 4:50 4:49 3:21 3:20 2:24 2:23 1:42 1:41 1:07 1:06 0:37 0:36 0:10 24:00 7:36 7:35 4:26 4:25 2:59 2:58 2:00 1:59 1:16 1:15 0:41 0:40 0:10 24:00 7:06 7:05 3:58 3:57 2:29 2:28 1:30 1:29 0:46 0:45 0:10 24:00 6:35 6:34 3:25 3:24 1:58 1:57 0:55 0:54 0:10 24:00 5:49 5:48 2:39 2:38 1:10 1:09 0:10 24:00 4:50 4:49 1:40 1:39 0:10 24:00 3:21 3:20 0:10 24:00 0:10 FIGURE 5-9. TABLE 2 – SURFACE INTERVAL TIME (SIT) TABLE.


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