A Comparison of Dive Tables

 In conjunction with the release of the Fifth Edition of the Enriched Air Nitrox Student Manual and Workbook IANTD has implemented the IAND, Inc. / Repetitive Diver, Inc. Diving and Decompression Tables (herein referred to as the IANTD Tables). IANTD will no longer be using the US Navy Air, NOAA I or NOAA II tables in the Basic Nitrox Diver Course. This change was implemented to provide continuity in the training of all IANTD divers. Currently, all IANTD courses use the Bühlmann ZH-L16 model for determining decompression obligation. These Bühlmann-based tables are among the most widely used dive tables in the world and the ZH-L16 system is used to calculate both staged and continuous decompression and is programmed into many of today’s dive computers.

 One of the most common comments IANTD receives from new users of these tables is that they are too conservative. When comparing the IANTD Air Table with the US NAVY Air Table, a diver will get more no-decompression dive time using the US NAVY Air Table, but only for the first dive. If the diver plans a repetitive dive it is noticed that typically there is more no-decompression dive time using the IANTD Air Table.

 In order to explain this further let’s look at a dive profile.

Dive # 1 will be to 80 fsw (24 msw) for the maximum no-decompression time limit.

We will use a 45 minute surface interval.

Dive # 2 will be to 60 fsw (18 msw) for the maximum no-decompression time limit as well.

First using the US Navy Air Table, let’s plan Dive # 1: 

80 fsw (24 msw) for 40 minutes = Repetitive Group I

45 minute surface interval = Repetitive Group H

And using the US Navy Air Table, let’s plan Dive # 2:

 60 fsw (18 msw)

Maximum bottom time = 60 minutes

Residual Nitrogen Time = 52 minutes

Actual bottom time = 60 - 52 = 8 minutes

Total actual time diving for two dives

 40 + 8 = 48 minutes

 

Dive #1

Table Type

IANTD Air

NAVY Air

 PADI Air

NAUI Air

IANTD 36%

Depth

fsw (msw)

 80 (24)

80 (24)

80 (24)

80 (24)

 80 (24)

Dive Time

25

 40

30

 35

 51

 Pressure Group

 E

I

 R

H

F

Surface Interval 45 minutes

A

H

I

G

C

Dive #2

Table Type

IANTD Air

 NAVY Air

PADI Air

 NAUI Air

 IANTD 40%

Depth

fsw (msw)

60 (18)

 60 (18)

 60 (18)

 60 (18)

60 (18)

Maximum No-Deco Time

51

60

 55

55

125

RNT

14

52

25

44

 37

Maximum Bottom Time

37

8

30

11

88

Dive #1

Dive Time

25

40

30

 35

51

Total Bottom Time for Dives
1 & 2

62

48

60

46

139

 

Now we will use the IANTD Air Table for comparison.

Dive #1

80 fsw (24 msw) for 25 minutes = Repetitive Group I

45 minute surface interval = Repetitive Group A

 

Dive # 2

60 fsw (18 msw)

Maximum bottom time = 51 minutes

Residual Nitrogen Time = 14 minutes

Actual bottom time = 51 - 14 = 37 minutes

Total actual time diving for two dives

 25 + 37 = 62 minutes

 Now look at the last column of the dive profiler which provides the diver with a comparison using the IANTD EANx Tables. Using a 36% mix on the first dive and a 40% mix on the second dive there is a Maximum No-Decompression Time of 139 minutes. That is almost three (3) times the amount of bottom time versus if this dive is made on Air using the US NAVY Air Tables.

 So when divers first look at the IANTD Tables it may appear that there is less time in the water, but it becomes obvious that whenever a repetitive dive is preferred, this may not be the case. Understand that the NAVY Air tables were designed for military purposes, i.e. long shallow single dives by 19 year old divers in top physical condition. The IANTD Tables are designed for all Divers – just like you and me...

Copyright © 1996 - 2002. All rights reserved.
This page was designed by IANTD TekHedz.