Published Tables

The risk of decompression sickness can be reduced by the conservative use of dive tables.

Note: Most tech divers still dive tables on deep dives because these dives are Trimix dives and there are no dive computers that currently work for Trimix dives. And, even when Trimix dive computers are available, tables will still be used to plan deep dives and as a backup to a failed Trimix dive computer. So, settle down and get comfortable with dive tables.

Begin with the selection of dive tables that are inherently safe. A good choice is tables derived from the Buhlmann model. Both the original Buhlmann tables and the DECOM computer generated Buhlmann tables are good choices. Use of the original USN tables is not recommended.

Note: The DECOM table below was generated using the DECOM 6.61 dive planning program. The "conservatism settings" for both Nitrogen and Helium were set at 7%.

US Navy Dive Tables (Air)
FSW	Bottom Time and Deco Stops
130	15	20	25	30
40
30
20				3
10	1	4	10	18

Buhlmann Dive Tables (Air)
FSW	Bottom Time and Deco Stops
130	15	20	25	30
40
30			2	3
20		3	4	7
10	4	7	12	18

DECOM Dive Tables (Air)
FSW	Bottom Time and Deco Stops
130	15	20	25	30
40				2
30		1	4	6
20	3	7	9	11
10	6	9	14	19

Using the DECOM dive table as an example, the interpretation of the table for a 130 FSW dive for 25 minutes is that you; dive to 130 FSW for 25 minutes, then ascend to your first stop at 30 FSW. There you stop for 4 minutes. Then you ascend to 20 FSW and stop for 9 minutes, etc., etc.

Note: Compare the difference between the US Navy table and either of the two Buhlmann tables and you will see that the US Navy stops are shallower and shorter. It is for this reason that the US Navy tables got the reputation for being the fastest to get you out of the water and the fastest to get you into a chamber. It is also for this reason that the use of the original USN tables is not recommended. In fact, even the US Navy has discontinued the use of these tables.

To add safety to the use of the selected tables, apply one or more of the approaches listed below. Remember, even the safest tables have some risk in them, so it’s not a good idea to "push" the tables.

Parameter	Approach	Actual Dive	Dive Table Plan
Maximum Depth	Use Next Deepest Depth	130 FSW Maximum Depth	140 FSW Table Depth
Bottom Time	Use Next Longest Time	25 minutes Bottom Time	30 minutes Table Time
Bottom Mix	Use More Oxygen	32% Bottom Mix	21% Table Plan
Deco Stops	Extend Shallowest Time	xx + 5 Minutes @ 10 FSW	xx Minutes @ 10 FSW
Deco Mix	Use More Oxygen	80 % Deco Mix	21 % Deco Mix

For example, to make the 130 FSW dive for 25 minutes, you could use the 140 foot air tables for 30 minutes of bottom time. Then, instead of doing the dive on air you could use EANx32 for the bottom mix and EANx80 for the decompression mix. And finally, you could extend the time spent on the shallowest decompression stop.

Employing all of these approaches on one dive would be overly conservative. However, every dive plan should have some additional safety built into it to avoid "pushing" the tables.

Note: Controlled ascent rates are crucial to proper off gassing. Most modern dive tables assume an ascent rate of 30 feet per minute. It is important that you do not ascend faster or slower than this rate. If you ascend faster you will off gas too rapidly and risk decompression sickness. If you ascend slower you will be at depth for a longer time than planned and again risk decompression sickness.

Warning

Ascend from every tech dive at 30 feet per minute.

Dive Tables
Published Tables
Self Test

Buhlmann model based dive tables are ___ than US Navy dive tables.

To add conservatism to a dive, plan it as deeper and longer than the actual dive you will do.

To add conservatism to a dive, add additional time to the shallowest decompression stop.

The proper ascent rate for tech diving is ____ feet per minute.