Within the scope of recreational diving, decompression diving is exclusively an emergency procedure. 

However there’s an important aspect to note about combining a dive that requires emergency decompression with repetitive dives:

it’s a bad idea.

A 1986 U.S. Navy test revealed an unacceptable rate of decompression sickness resulting from repetitive decompression dives,

despite table predictions.  Furthermore, anecdotal reports from recompression chamber facilities indicate

many cases of decompression sickness result from combining decompression diving with repetitive diving. 

Apparently, even if only one dive in the series is a decompression dive, the probability of decompression sickness increases.

It seems that in many cases, mathematical decompression models cant’ adequately predict the combination of a repetitive dive with a decompression dive. 

For this reason, avoid combining a dive that requires emergency decompression with a repetitive dive. 

If you make a dive and accidentally end up at an emergency stop, after the stop make that the last dive of the day,

even if your computer permits more dives.  (The Wheel requires at least a six our surface interval).

 

 

It’s your dive computer that really makes multilevel diving practical.  While The Wheel makes it possible without a computer,

the primary advantage of using a computer for multilevel diving is that it computes your exact dive profile for maximum allowable no stop time. 

The Wheel helps you understand how a computer calculates, and it’s your best option for resuming diving if your computer crashes (it happens),

but 99 percent of the time, you’ll probably want to use your computer for the convenience and the precision it offers.

However, as wondrous as your computer is, it’s imperative that you make computer-assisted, not computer controlled dives. 

Computers appear almost magical to some people; but they’re just highly sophisticated calculators that read the depth and time and then apply

the same type decompression model your dive tables, and the same guidelines apply to computer diving as to table diving.

Eight rules for computer diving (some of these apply to tables, too) help you stay within the limits of what has been proven

to produce an acceptably minimal probability of decompression sickness. 

1.    Don’t dive to the no decompression limits and avoid mandatory emergency decompression. 

Stay well within the computers limits.  You should have ample time before reaching a no stop limit at all times during your dive.

2. Topography permitting make multilevel dives that start deep and work shallower. 

Avoid ‘sawtooth’ dive profiles with repeated significant shallow and deep depth changes, such as starting a dive at 30 meters/100 feet,

then ascending to 18 meters/60 feet and after a while descending to 28 meters/90 feet. 

While its unclear what added risk there may be for this kind of diving,

if any within the realm of no stop diving the vast majority of test data is based on ‘forward’ profiles that start deep and work progressively upward. 

To stay within the envelope of proved test data, start at the deepest point and progress shallower (minor variations aren’t a problem). 

Your computer may permit sawtooth profiles by calculating them, not to encourage this kind of profile, but so you have information if you accidentally do one.

 

3. Control your rate of ascent to 18 meters/60 feet per minute or slower. 

Virtually all computers have rate indicators that alert you if you start to go too fast.

4. Take a safety stop at the end of all dives at 5 meters/15 feet for at least 3 minutes.

5. Allow a surface interval of at least 60 minutes with a computer; even if it permits the dive time you want in less time.

6. Limit repetitive dives to 30 meters/100 feet or less.  Make your deepest dive first, with subsequent dives progressively shallower.

7. Don’t get so caught up in your extended bottom time limit that you neglect your air supply.

8. Be aware that no computer or table can account for physiological variations caused by factors such as age, dehydration, alcohol consumption,

strenuous exercise, excessive fat tissue, injury or other factors that predispose you toward decompression sickness.

The more of these factors that apply, the more conservatively you should use your computer or table. 

Surprisingly, being conservative doesn’t always mean you have to cut your dive short- usually,

you can simply move shallower sooner so you always have lots of time before reaching a no decompression limit. 

 

 

Equipment for all multilevel dives
Besides the equipment you normally wear in your local dive environment,

you want to have three pieces of equipment along for multilevel dives.

The Wheel. As the table you can plan multilevel dives with, The Wheel is recommended for two reasons. 

First, to plan a multilevel dive with or without your computer. 

The Wheel will give you a rough idea of what your computer will allow as you ascend during the course of the dive.

Second, if your computer goes south on you, use The Wheel as a back up that permits multilevel diving –

something you’ll want especially if all your buddies are still humming along fine. 

If you’re on an exotic dive holiday and your computer quits, you’ll kick yourself up and down the dock for leaving your wheel at home.

Depth gauge and timer.  These two pieces of equipment are necessary to back up a dive computer. 

You’ll also need these to multilevel dive with The Wheel without your computer.

 

 

Sunrise Diving, Phuket, Thailand.

PADI 5 Star National Geographic Instructor Development Center.