Comparison of Dive Plans using Air and EAN36
Diver 1: Air Diver 2: EAN36
NAUI Dive Tables
For example, a diver making an initial dive to 27 meters
(90 feet) using air would have a maximum dive time of
25 minutes on the NAUI Dive Tables. The same diver
using a nitrox mix with 36% oxygen (EAN36) would
have a maximum dive time of 50 minutes on the NAUI
EAN36 Dive Tables. Using the NAUI Reduced Gradient
Bubble Model (RGBM) Tables, the diver would have 25
minutes if using air and 46 minutes if using EAN36.
Nitrox has advantages in repetitive dives. Looking at
a typical recreational dive profile, let’s compare a series
of two dives: one diver is breathing air, and the other
diver is breathing EAN36. The first dive is to 24 meters
(80 feet) for 30 minutes. After a one-hour surface interval,
the second dive will be to 17 meters (55 feet).
Diver one, using air and NAUI Dive Tables, emerges
from the first dive with a Letter Group of G. One hour
later, entering the water as an “F diver,” the diver has
an adjusted maximum dive time of 19 minutes for the
17-meter (55-foot) dive. If the diver is using the NAUI
RGBM Tables, he has a maximum dive time of 55 minutes
for the second dive.
Chapter 1- Introduction
Diver two, using EAN36 and NAUI EAN36 Dive
Tables, finishes the first dive with a Letter Group of F.
One hour later, she begins the second dive as an “E
diver.” She has an adjusted maximum dive time of 62
minutes for her 17 meters (55 feet) dive. If using the
NAUI RGBM EAN36 Tables, she would have a maximum
dive time of 115 minutes!
On the second dive, the diver using enriched air
nitrox has a 43-minute advantage over the diver using air
if using the NAUI Dive Tables or a 60-minute advantage if
using the NAUI RGBM Tables.
Another benefit of nitrox is the possibility of a shorter
required surface interval. In the example above, the
nitrox diver has 62 minutes available dive time after a
one-hour surface interval if using the NAUI Dive Tables. If
the air diver using the same tables wanted to have a dive
time of 30 minutes, he would have to attain a Letter
Group of D before beginning the second dive. To move
from “G” to “D” requires a surface interval time of at
least 2 hours 59 minutes! The NAUI RGBM Tables are
based on a one-hour surface interval, so those numbers
do not change.
First Dive
24 meters (80 feet)
Dive Time: 30 minutes
Ending Group: G
One hour surface interval
Entering Group: F
Second Dive
17 meters (55 feet)
Max. Dive Time:
19 minutes
NAUI RGBM Tables
First Dive
24 meters (80 feet)
Dive Time: 30 minutes
One hour surface interval
Second Dive
17 meters (55 feet)
Max. Dive Time:
55 minutes
NAUI Dive Tables
First Dive
24 meters (80 feet)
Dive Time: 30 minutes
Ending Group: F
One hour surface interval
Entering Group: E
Second Dive
17 meters (55 feet)
Max. Dive Time:
62 minutes
NAUI RGBM Tables
First Dive
24 meters (80 feet)
Dive Time: 30 minutes
One hour surface interval
Second Dive
17 meters (55 feet)
Max. Dive Time:
115 minutes
Introduction
9
FIGURE 1-4: A COMPARISON OF DIVE PLANS SHOWING THE DIVE TIME ADVANTAGE USING NITROX–THE DIVER BREATHING EAN36 HAS
SIGNIFICANTLY GREATER NO-DECOMPRESSION TIME THAN THE AIR DIVER