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Decompression, Dive Tables, and Dive Computers Dive Tables n The purpose of this presentation is to review the use of the NAUI Dive Tables. n It is best.

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Presentation on theme: "Decompression, Dive Tables, and Dive Computers Dive Tables n The purpose of this presentation is to review the use of the NAUI Dive Tables. n It is best."— Presentation transcript:

1 Decompression, Dive Tables, and Dive Computers Dive Tables n The purpose of this presentation is to review the use of the NAUI Dive Tables. n It is best if you have a copy of the NAUI Dive Tables while you work through this presentation n You can print out a copy of the tables at the My Scuba Tutor section of our web site –

2 Decompression, Dive Tables, and Dive Computers Definitions To Know n Actual Dive Time (ADT) – Time calculated from the beginning of the descent to the return to the surface, less the safety stop. n Maximum Dive Time (MDT) – The maximum time you can spend at a given depth without the need to decompress. n Depth – The maximum depth reached during the dive. n Repetitive Dive – Any subsequent dive within 24 hours of a previous dive. n Repetitive Dive Group – A letter designation indicating the amount of nitrogen remaining in a divers body from the previous dive or dives. n Repetitive Nitrogen Time (RNT) – The amount of nitrogen remaining in the body expressed in minutes. This time must be counted as part of the current dive. It is like a penalty. You do not get to dive it but you must count it.

3 Decompression, Dive Tables, and Dive Computers Definitions To Know (continued) n Total Nitrogen Time (TNT) – Total amount of nitrogen in a divers body. This includes Actual Dive Time Plus Residual Dive Time; i.e. ADT + RNT = TNT n Adjusted Maximum Dive Time (AMDT) – Maximum dive time adjusted for previous dives by deducting residual dive time. n Surface Interval Time (SIT) – Time between dives. Must be at least 10 minutes to count as surface interval. n Safety Stop – Three minute stop at 15 feet. Not mandatory but highly recommended. n Decompression Stop – Mandatory stop. Usually performed at 15 feet, but deeper stops could be required n Planned Depth (PD) – Planned depth of next dive. n Planned Depth Plus (PD+) Planned depth of next dive plus 10 feet.

4 Decompression, Dive Tables, and Dive Computers Residual Nitrogen To properly use dive tables and dive computers, you must understand the concept of residual nitrogen. n Residual nitrogen reduces your time limits for any given depth on your next dive. Each successive dive will add additional residual nitrogen and reduce the no decompression time allowed on the next dive. Note how the nitrogen levels drop during the surface intervals but build from that point during the next dive.

5 Decompression, Dive Tables, and Dive Computers Dive Table Overview The NAUI Dive Tables use a Letter Group designation to express the amount of residual nitrogen in your body. n The letters range from A to L.

6 Decompression, Dive Tables, and Dive Computers Dive Table Terms The following apply to the NAUI Dive Tables: n Maximum Dive Time (MDT) Shown as a number inside a circle inside a square. n Decompression Stop Shown as a number above a blue box indicating depth of stop.

7 Decompression, Dive Tables, and Dive Computers Dive Table Rules You must understand the following dive table rules completely. n Ascend no faster than 30 feet per minute. n Use exact or next greater number listed for your depth. n Use exact or next greater number listed for your time.

8 Decompression, Dive Tables, and Dive Computers Dive Table Rules continued You must understand the following dive table rules completely. n Use the deepest depth you reach during your dive. n Always make your deepest dive first. n Dives shallower than 40 feet are planned as 40 feet.

9 Decompression, Dive Tables, and Dive Computers Dive Table Rules continued You must understand the following dive table rules completely. n Surface interval time must be at least 10 minutes. n Use the next greater dive time if it was cold or strenuous. n Avoid dives that take you to the no-decompression limit.

10 Decompression, Dive Tables, and Dive Computers Dive Table Organization The NAUI dive tables are composed of three tables. n Table 1: End of Dive Letter Group (for the current dive – 60 feet for 40 minutes). Start where it says Start (Left side of right table.) Go down the depth column to 60 feet, then across the time row to 40 minutes. The go down from 40 feet to find the letter group indicating the amount of nitrogen in you body.

11 Decompression, Dive Tables, and Dive Computers Review on Dive Table 1 What have you learned so far? n List the Group Letters for the following dive profiles: n If you do a dive to 18 meters (60 feet) for 42 minutes. n If you do a dive to 12 meters (40 feet) for 88 minutes. n If you do a dive to 36 meters (120 feet) for 9 minutes. n Answers: H, I, D

12 Decompression, Dive Tables, and Dive Computers Dive Table Organization The NAUI dive tables are composed of three tables. n Table 2: Surface Interval Time (SIT) Table. Start with the repetitive group from the end of your first dive and continue down that column (following the arrows) until you find the block of time that your surface interval fits into. Then follow that row to your left to find your new letter group.

13 Decompression, Dive Tables, and Dive Computers Review on Dive Table 2 What have you learned so far? n List the new Group Letters for the following Surface Interval Times: n You have a group letter of I and your SIT is 2 hours and 36 minutes. n You have a group letter of C and your SIT is 3 hours. n You have a group letter of G and your SIT is 42 minutes. n Answers: E, B, F

14 Decompression, Dive Tables, and Dive Computers Dive Table Organization The NAUI dive tables are composed of three tables. n Table 3: Repetitive Dive Timetable. Continue across the new groups row until you reach the column indicating the depth of your repetitive dive. The note your AMDT and RNT. The footnote at the bottom of the chart shows which is which.

15 Decompression, Dive Tables, and Dive Computers Review on Dive Table 3 What have you learned so far? Answer the following questions. n1. If you have a beginning Letter Group of D and you want to dive to 18 meters (60 feet), your AMDT is _____ minutes. n2. If you have a new letter group of B and you want to dive to 27 meters (90 feet), your AMDT is _____ minutes. n3. If you have a beginning letter group of G, you can dive to 24 meters (80 feet) for _____ minutes. n4. If you have a beginning Letter Group of E and you dive to 17 meters (57 feet), your RNT is _____ minutes. n5. If you have a beginning Letter Group of G and you dive to 11 meters (37 feet), your RNT is _____ minutes. n6. If you have a beginning Letter Group of C and you dive to 20 meters (67 feet) for 22 minutes, your TNT is _____ minutes. n7. If you have a beginning Letter Group of D and you dive to 16.2 meters (54 feet) for 18 minutes, your TNT is _____ minutes. nAnswers: 31, 18, 0, 30, 73, 37, 42

16 Decompression, Dive Tables, and Dive Computers Dive Planning Worksheet You must systematically keep track of your dive information when working with NAUI Dive Tables. n Planning your dive. n Finding your letter group. n Recording your SIT and finding your new group letter. n Planning your repetitive dive. n Recording your repetitive dive. n Always diagram your dive.

17 Decompression, Dive Tables, and Dive Computers Review on Dive Tables Review the following problems using your planning worksheet. If you do not have one, you can print it from My Tutor. 1. Your first dive of the day was to 20 meters (66 feet). You descended at 9:40, surfaced at 10:19, and completed a 3-minute precautionary decompression stop (ADT=36). Your second dive was to 14 meters (46 feet). You descended at 12:32, surfaced at 1:13, and completed a 3- minute precautionary decompression stop (ADT=38). Your third dive was to 12 meters (40 feet). You descended at 2:43, surfaced at 3:26, and completed a 3-minute precautionary decompression stop (ADT=40). 2. Your first dive of the second day of your trip was to 24 meters (80 feet). You descended at 8:35, surfaced at 8:58, and completed a 3-minute precautionary decompression stop (ADT=20). Your SIT was 2 hours and 46 minutes. Your second dive was to 16 meters (52.5 feet) for 36 minutes including your precautionary decompression stop (ADT=33). You surfaced at 12:20. Your third dive was to 10 meters (33 feet). You descended at 3:10, surfaced at 4:10, and completed a 3-minute precautionary decompression stop (ADT=57).

18 Decompression, Dive Tables, and Dive Computers Maximizing Underwater Time You cam maximize your dive time by adjusting your SIT, your depth, or your ADT. n Limiting your dive time means you absorb less nitrogen during that dive. n Increasing your surface interval allows you to outgas more nitrogen, reducing your residual nitrogen times. n Limiting your depth reduces your nitrogen uptake during that dive.

19 Decompression, Dive Tables, and Dive Computers Special Rules There are a number procedures you must learn to handle special situations. Discuss these with your instructor. n Decompression diving. n Precautionary decompression stops. n Required decompression. n Omitted decompression. n Cold or strenuous dives. n Flying after diving. n Altitude diving.


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