for a PO2 of 1.6 ata. Therefore, the NAUI EAN36 Dive
Tables have a maximum depth of 33 meters (110 feet).
The NAUI Nitrox Dive Tables have a tolerance of ±1%.
The EAN32 Dive Tables can be used for nitrox blends
from 31% to 33% oxygen; and the EAN36 Dive Tables,
for blends from 35% to 37% oxygen.
The usual dive table rules and precautions apply
when using the NAUI Nitrox Dive Tables.
• Treat each dive as a square profile dive, with the
deepest point reached on the dive being used as
the depth for the whole dive.
• If the exact depth or time does not appear on the
table, round up to the next greater number.
• The tables assume an ascent rate of 9 meters (30
feet) per minute.
• Planning repetitive dives progressively shallower
will yield shorter required surface interval times.
• The required surface interval between two separate
dives is 10 minutes; the recommended minimum
surface interval is one hour.
• The tables are designed to be used at sea-level
atmospheric pressure, and adjustments must be
made for altitudes above about 300 meters (1000
feet).
• If flying or ascending to altitude after diving, wait
12 hours after a single dive and 18 hours after a
series of repetitive dives.
While using NAUI’s prepared tables is the easiest
way to plan dives, the three NAUI standard tables–Air,
EAN32, and EAN36 Dive Tables–do not always yield
interchangeable results. Divers using these tables should
not move from one table to a richer oxygen table in any
repetitive dive series. The tables actually assume that the
diver will be using the same gas mixture throughout.
You can change from beginning with air to EAN32 or
EAN36 and continue to use the air tables. You can
switch from initial use of EAN32 to EAN36 and continue
to use the EAN32 table. This limitation is not the case
with the NAUI RGBM Tables with which you can switch
mixtures and tables from dive to dive.
In order to effectively and safely switch between gas
mixes or to use nitrox blends not encompassed by the
EAN32 and EAN36 tables, you should use equivalent air
Chapter 5 - Dive Tables and Dive Computers
depth (EAD). By applying the equivalent air depth formula
to your diving, you can use any standard air tables
as long as you also follow oxygen exposure limits.
EQUIVALENT AIR DEPTH AND STANDARD AIR
DIVE TABLES
As noted earlier, equivalent air depth (EAD) is determined
by the partial pressure of nitrogen that the diver
is actually breathing. Because nitrox has a lower fraction
of nitrogen than air, the nitrogen partial pressure
will also be less than with air for any given depth, and
the diver’s equivalent depth for nitrogen absorption will
also be less than with air. It is not the actual depth, but
the partial pressure of nitrogen in the breathing gas that
matters.
The theory behind equivalent air depth is that an
EAN diver’s exposure to nitrogen for any absolute pressure
(depth) will be proportionally less than with air as
the fraction of nitrogen in the mix is less than 0.79 (the
fraction of nitrogen in air). Moreover, the rate at which
nitrogen is absorbed by the various tissues is related to
Dive Tables and Dive Computers
57
FIGURE 5-4: NAUI AIR DIVE TABLES