Rebreather Rules for Survival

In 2001, Andy Holman and I began a technical diving club in Southern California which did not go anywhere.  However, as part of our effort we compiled a few documents to help provide resources for the members and the general public.  I recently came across them.

This was produced to help rebreather divers in the group.  It is principally geared toward technical rebreather diving, but holds many very current points for recreational rebreather divers as well.

Not all components are current, deep stops are in question and there is growing evidence that some applications may no longer be best practice.

Would you add anything?  Remove anything?

There is a lot of common repetition between this document and the Open Circuit Rules as they are both meant to stand alone. Open Circuit Rules are here.

Rebreather Rules of Survival  (R2S)

  • 1.     Equipment

Maintain and prepare equipment a few days before dive day.

Leave unit on and gas on until on the boat and dekitting.

Don’t dive if equipment is not 100% working.

Don’t push limits of gas, absorbent, batteries, and your energy.

Be willing to ditch the dive or dive trip.

Take a spare OC rig, to switch over to, if in doubt.

Carry enough OC bailout to complete OC deco from furthest/worst point in the dive.

Do repeated FLAGS tests.

Ensure weight release configuration works.

Be willing to dump unit or gear to save your life.

Always conduct predive with a checklist in hand.

Always follow the checklist in a low stress and low distraction environment.

Always conduct a negative and a positive pressure check.

Never dive unless all three sensors are working.

Prebreathe the unit for confirmation of functionality.

Complete post dive checks with a checklist in hand.

Make sure you clean your rebreather properly each day.  Not all cleaners are created equal and many simply do not work.

Your rebreather is an extension of your own physiology, best to not put anything in your rebreather you would not want in you.

2.     Predive Planning

Make sure all variables are accounted for before entering the water. Complete accounting of oxygen, decompression, inert gasses, gas management, thermal exposure, mission, and logistics must be known for each diver in the team.

The following questions should be answered.


What is the planned PO2 for the dive?

What is the CNS and Pulmonary exposure?

Is there a better choice for set point?

Do I need to conduct a set point switch?

How do I plan to avoid Hyperoxia?

How do I plan to prevent Hypoxia?

What PO2 should I have in my diluent?

What PO2 should I have in my OC bailout?

Can you complete OC bailout with these PO2s?


What system will I use to safely control decompression on the dive? (EAD, Set Point Table, Air Computer, Nitrox Computer, Multi-gas computer, Constant PO2 computer, or Custom table)

What decompression obligation am I able to handle?

Am I qualified, willing, prepared, and able to do this level of decompression?

What will I do if the unit fails and I have to decompress on OC?

What contingency tables or backup do I use?

How do I plan on accomplishing decompression?

What method do I plan to use to communicate with the surface?

Where will I conduct decompression?

Inert Gasses:

Have I packed the canister properly?

Do I know exactly how much time I have on my absorbent already?

Has the absorbent settled after transport?

How much time do I have available for this dive with my absorbent?

Have I done anything that might cause absorbent channeling or failure?

Have I accounted for my CO2 production?

Have I accounted for temperature?

What level of narcosis have I planned for?

Am I comfortable with that level of narcosis?

Will I exceed crossover depth for my chosen PO2?

Is there a better choice for my diluent?

Gas Management:

Do I have enough oxygen to complete the dive?

Do I have enough diluent to complete the dive?

Have I accounted for the proper reserves?

Do I have the proper gas supply for OC bailout?

How will I inflate my drysuit?

How will I inflate my liftbag or SMB?


Am I properly insulated to complete the entire dive in relative comfort? (Losing heat can be as deadly as losing gas or not completing deco.)

Is a wetsuit proper for this exposure?

How will I supply gas to my drysuit?

Do I need argon?

How will I supply argon to my suit?

What is the bottom temperature?

What is the temperature I will be decompressing in?

Do I have the thermal tolerance to complete this dive?


Is this dive worth doing?

Should I be doing this dive?

What is the plan for the bottom?

Am I prepared for the bottom activity?

Do I have the necessary tools to be successful on the bottom?

Do I have the necessary skills and experience to do this dive with confidence?

Who is my team?

Am I comfortable with my team?

Does this dive require surface rehearsal?

Does this dive require dedicated surface support?

How am I being deployed on the dive?

How am I descending on the dive?

What is my priority list for the bottom?

What is my runtime for this dive?

When do I need to be off the bottom?

How am I ascending from the bottom?

How will I complete deco safely?

How will I communicate with the surface?

Do my support divers know how, when, and where to reach me?

Do I need to plan for any special procedures during deco?

How do I plan to handle gas switches if I make any?

How do I plan to communicate with my teammates?

How do I plan to deploy my liftbag or SMB?

Do I remember that deco is the longest part of the dive?

Do I remember that the dive is not over when I start deco and it is just beginning?

How will I handle OC bailout?

How do I plan to abort this dive?

How can this fail?


Do I have the absorbent I need to for all my diving?

Do I have all the gasses I need to do all my diving?

Do I have the platform necessary to be successful on this dive?

Do I have sufficient support for this dive?

Do I feel comfortable with everyone who will be on this dive?

3.     Drills while diving

Start of the dive, flush the unit with 100% 02 to validate PO2 readings and for surface activity.

Check all gas on, breathable mixture, unit on, mouthpiece in, exhale, then open before descending or entering the water on the unit.

Check the manual diluent add valve before descending.

Descend slowly.

Always do buddy check on the surface and a bubble check at 15ft.

Always know your PO2, Master every 2 minutes, Slave every 4 min.

Monitor primary and secondary displays.  You should always know your PO2.

Be aware of unexpected buoyancy changes or noise.

Use one breath in the bag constant volume monitoring.

Do a bailout drill at beginning and end of every dive.

At deco 15ft flush the unit with 100% 02 to validate PO2 readings and for surface activity. Ascend slowly.

Fully inflate BCD just before surfacing and opening loop.

Continue to breath 100% 02 while dekitting.

4.     Avoid Stress

Avoid rushing into water, rushing to put equipment on.

Time pressure will kill you!

There is always time for buddy check, bubble check.

Avoid equipment loading, buddy pressure.

Choose a patient Buddy.

5.     Are you solo diving

Watch your buddy to make sure your buddy is watching you.

Test your buddy (If you can count to 200 between buddy eye contacts your buddy will not save you).

Don’t solo dive.  Your qualified buddy is the last chance to save you.

If you solo dive be cautious, monitor PO2 more often.

The only time you and your buddy are safe is on the boat sitting down or on land out of the water.

Use constant and consistent communications throughout the dive.

Carry extra OC bailout.

There is no backup brain!

6.     Complacency

Watch for over confidence. Know your PO2 at all times.

If you are an expert technical diver, you are still a novice on a rebreather.  Do 100 dives above 100ft, before going deeper.

Workup to depth slowly from there, baby steps will save your life.

At the wrong time, the unit will bite you in the butt.  (Murphy’s/Sods Law)

Pyle’s Law:  at 50 hours you think you are hot stuff, at 100 hours you think you are there, at 150 hours you realize what a weenie you have been getting to 150 hours.

Other Rules

1. After you clear your 20-fsw stop (combining the 10-20 fsw stops for 1.6 PPO2) ascend at 1 fpm until you get to the surface.

2. Remove all gear and breathe while at the surface while still in the water…if possible for about 10 min.

3. Have a portable chamber on the boat if you are 220+ miles from land.

4. Don’t switch off Helium based mixes until 50-foot stop.

5. Have a back-up rebreather on the boat to allow surface support to replace a malfunctioning unit with the inflation of a specific colored lift bag.

6. Dives below 250 feet (75M) should not be conducted if unsupported.  If the exposures are long on shallower dives, they should be supported as well.

7. In open water operations, it is better to conduct multiple dives to depth rather than one long exposure.  The uncertain conditions in the ocean expose the diver to too much risks if decompression obligations are long.

8. Only you can control your dive.  The only mission that matters on any dive is that all return safely.  Nothing is worth dying for on a dive, including someone else.

Conclusion: OC is like a bicycle and CCR is like a helicopter both are transportation.  Bicycles work nearly all the time and its not a big problem if it does not, you walk.  You can abuse the bicycle and it keeps on working.  Helicopters you need to preflight test, watch the gas, watch gauges, be in control at all times, otherwise you will crash and die.  Riding a bike does not mean you can fly a helicopter…..

One Comment on “Rebreather Rules for Survival”

  1. […] ← Rebreather Rules for Survival Rebreather Forum 3.0 […]

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