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…..

Rebreather Forum 3.0

Rebreather Forum 3.0 brought together the leaders and shakers in the rebreather world May 18 – 20, 2012.  The event took place in Orlando, Florida at the Caribe Royale Hotel Convention Center.  Participants from around the world gathered to listen to and participate in presentations in three areas of concentration, incidents, design and testing, and operations and training.  The event had over 400 attendees.

The last rebreather forum occurred in 1996 in California.  The sixteen years that have passed since that event have brought with it many substantive changes within the industry.  This meeting would challenge old thinking and consider if the foundational questions had changed much at all.

The forum’s objectives were stated as follows,  (

“To establish the state of the art of rebreather diving, and where appropriate, to make recommendations in the following areas:

  • To codify the state of the art of rebreather use, including issues such as ventilatory characteristics, oxygen control, CO2 control, automation, warnings, bail-out system, redundancy and backup systems.
  • To review available data for accident analysis and avoidance.
  • To review training and operational protocols.
  • To examine considerations for conducting extreme exposure dives.”

The event was made up of a preamble Explorer Day followed by two and half days of forum events.  The Explorer Day allowed participants to “try dive” units of their choice in the hotel pool.  AP Valves, Revo, Titan, Inner Space, and several other manufacturers participated in the demos.  The presentations were broken into three concurrent tracks with various talks of a half hour to one hour in length.  These tracks focused on general rebreather topics, rebreather medicine and physiology, and rebreather business and operations.   There was a ready supply of enthusiastic newcomers to rebreathers with many demo participants having never tried a rebreather before.

All of the presentations were standing room only with some stretched for space.  Notable speakers like Richard Pyle spoke on his diving with rebreathers and the evolution he has seen since the last rebreather forum.  Dr. Simon Mitchell presented on CCR Physiology.  Jill Heinerth put forward her Five Golden Rules for rebreather diving.  Richie Kohler talked about the importance of checklists.  James Morgan showed why he stopped blowing bubbles, well sometimes stops blowing bubbles.   Evan Kovacs got the audience very close to the action of his film subjects with the help of rebreathers.  One big surprise was when training agencies TDI, IANTD and ANDI shared their certification data regarding rebreathers in an open session planting the seed for open sharing in the future with all agencies.

Jill said, “RB3.0 was the most important gathering of technical divers that I have ever attended. The rebreather community has finally reached critical mass, allowing participants to express their opinions and move the industry forward in safety and transparency in a way we have not seen before.”

The forum program proceeded in the evening after the Explorer Day.  The forum format changed to a single track of presentations in the large ballroom.  Dr. Drew Richardson opened the forum.  Michael Menduno provided a retrospective of what has been learned from Rebreather Forum 2 with many of the players from that event present at the current event.  Dr. Richard “Harry” Harris led us through his inspiring deep work in New Zealand and Australian caves with an emphasis in overcoming obstacles in exploration.  The evening wrapped up with a panel on different user groups within the rebreather community.  In a stark contrast to previous events, the US Navy openly shared their user data and incident rates.

Supervisor of US Navy Diving, Commander Runkle, presented diving statistics for the 2011 year of diving.  The US Navy conducted 105,463 dives with a total of 5,503,406 minutes of Total Bottom Time.  Twenty-six incidences were reported.  Forty-four percent were related to rebreathers with the remainder being related to open circuit scuba and chamber operations.

During the previous five years the majority of incidents with navel rebreather use were related to lung trauma with forty-one percent attributed to air gas embolism.  Most of these related to the use of oxygen rebreathers.  This is the first time the navy has been so open with their data.  This should allow researchers to begin to establish a denominator related to rebreather use and incidences in at least this population of users.

Day two

A focus on incidents brought the morning to a humbling beginning.  Chaired by Dr. Petar Denoble, DAN’s incident guru, the sessions were focused on what the origins and results of fatalities and near miss incidents have been thus far.  Dr. Andrew Fock gave an overview of CCR Diving Fatalities and review of known events.  Lawyer David Concannon spoke to the legal cases that have arisen from incidents.  He reviewed cases he has defended and spoke to the need to pay more attention to triggering events that lead to fatalities rather than just the end result of the fatality.

Dr. Bill Stone spoke to the hazard analysis and human factors he investigated in the original development of the Cis Lunar and the continued efforts he has conducted with the Mk 6 and Poseidon’s new tech rig.  He began his presentation with the announcement of a landmark agreement between Poseidon and DAN to house all Mk 6 data that they have and into the future.  He then introduced his topic by saying; “We are leaving the cowboy era in rebreathers.”

Bill approaches rebreathers with the same mindset as he does when working on projects with NASA.  His analysis compared failure modes for open circuit to closed circuit.  The development of machines that can recognize and deal with variable environments and problem solves was illustrated by his footage of the self-driving car work he conducted with NASA.  Putting the Google car to shame, this vehicle can drive itself and recognize appropriate paths off road.  Many of these projects have lent ideas and technologies for the “smart systems” being incorporated into today’s rebreathers.  This is one of the big changes since the last forum.

This wrapped up the segment on incidents.  What was clear from the morning was that there can be advances in technologies and smart systems, but engineering will not remove the diver from the system.  Recreational diving will always be diver dependent.  You cannot engineer the diver out of the system.  So, there is also a need to focus on fixing the diver on all levels.  This places a high standard on training and community development.  If the user base is going to grow quickly a focus on this will be more necessary than ever before.

Focus Zone 2 revolved around design and testing.  Chaired by NEDU’s Dr. John Clarke, this focus area occupied the majority of the event.  Martin Parker of AP Values spoke about real time monitoring.  The talk was highlighted by a discussion of the systems they incorporated into James Cameron’s Deep Explorer sub for his successful dive to the deepest depths of the ocean.

Dr. Arne Sieber presented on oxygen sensor technologies.  Current sensor technologies have not changed much for a long time.  There are pressures to change sensors to comply with environmental laws that may make them incompatible with rebreather use.  This is scary news for rebreather divers.  The good news is that new technologies are being developed that could be available soon.  Data was presented that sensors are much more temperature sensitive than most would believe.  So, special care should be used when dealing with lower temperature environments.  Also, real time in mouthpiece oxygen and carbon dioxide monitoring has been beta tested.  Not ready for inclusion in production units yet, it speaks to a bright near future for improving this vulnerable area of the technology.

Kevin Gurr reported on online research he conducted into rebreather diver behaviors.  Results were self-reported by rebreather divers.  Scary data resulted.  A large number of divers were ignorant to the units they were diving and owned.  Simple capabilities and confusion about durations and depth limits were clear.  Sixty-four percent of those that self reported symptoms of carbon dioxide issues did not bailout nor did they end the dive.  The second half of his presentation focused on carbon dioxide sensors.  He believes we are four to five years away from real time in mouthpiece monitoring on production units.

Dr. Dan Warkander of the US Navy’s Experimental Diving Unit (NEDU) talked about carbon dioxide scrubber technology.  Dan spoke to the need for clear understanding of scrubber capabilities for temperature, workload, and depth with more available information from manufacturers to help divers make intelligent decisions about duration.   He presented data from navy tests that illustrate that canister durations can vary as much as five to twenty times based on temperature, depth, and workload.  Pointing to the importance to know the numbers for the unit being dived and the conditions it is being dived in.

Bruce Partridge of Shearwater fame finished up the day presenting on information technologies and the incorporation of real time data tracking into rebreather systems.  Bruce illustrated that no IT solution or mitigation designed into a rebreather can replace the need for checklists.  He did a wonderful job looking at how other industries have dealt with risk and how it was mitigated.   It is clear that a lot more data tracking is in the future.

The evening concluded with a gala dinner.  The keynote speaker was Dr. Michael Gernhardt, a NASA astronaut and diver, talked about exploration from sea to space and back.  The primary focus of his work has been on decompression modeling and space suit design.  More recently he has been working on the mission to mars and the more recent focus on near asteroid exploration.  Video of the mission testing brought the technology to life.  The presentation was a fascinating look at the future of space exploration with exciting possibilities of spin off benefits for rebreathers in the future.

Day 3

Dr. John Clarke continued chairing his focus area on testing.  Dr. Nigel Jones spoke about oxygen control.  Gavin Anthony and Mike Ward talked about pre-market testing.  Third party testing of units is the only way to verify the data provided is unbiased and can be trustworthy.  It is required of CE compliant units and the standard by which most have relied for decades.  Luckily, it is far more common today than at the time of the last forum.

Vince Ferris of NEDU and Oskar Franberg of Sweden presented on post incident testing of rebreathers.  The need for resources for analysis of rebreathers after an incident is clear.  Both of these gentlemen do this for their respective navies.  Civilian resources are limited and there is a clear need for resources to assist when there is an incident.

Dr. John Clarke closed the focus session with his favorite topic, semi closed rebreathers.  He playfully pointed out that the ultimate rebreather is the earth.  His work at the NEDU has allowed John to see and experiment with so many units and technologies that it is remarkable how broad his knowledge spans.  He pointed to some of the newer technologies possibly making semi closed rebreathers an option in the sport market.

After lunch focus zone 3 began concentrating on operations and training.  Phil Short chaired the session.  First up was a panel chaired by Dr. Jeff Bozanic on operations.  Dr. Richard Pyle discussed the history of his “twilight zone” fish collecting in the mesophotoic region.  He has a return on time of twelve new species of fish for every hour of bottom time.  He has also seen that for these deep technical dives open circuit requires over twice the hours of support than that of closed circuit.

US Park Service has found that rebreathers have increase work productivity by thirty-two percent over open circuit.  Most of the work being done is in the fifty to one hundred feet ranges.

An entertaining segment of the panel was a presentation on opinion versus science.  Those on the inside of rebreather understand well that opinion and science can be tough to distinguish when it comes to this topic.  The question still remains; will opinion or science dictate policies for rebreathers in the future?

Jill Jeinerth and Terrence Tysall chaired the final presentation focused on training.  Rather than having a traditional panel they decided to have a series of questions with audience participation to help answer them.  The majority of time was spent on the question of how to encourage or drive the use of checklists.  The root of the discussion was how to drive community behavior and move away from complacency.  A difficult question under any circumstances with the hopes of massive increases in users the timing is critical to address the issue.

How can you drive change in cultural bias when that bias is not good for diver outcomes?  Some hopes were presented for engineering that would require the behavior or not allow diving.  Some pointed to increased strictness in training requirements.  But, in the end, there is nothing that can make a diver not be complacent.  Attitude can be modeled, but not trained.

So, although these solutions can contribute to a new cultural bias, they cannot make it happen.  The diver cannot be engineered out of the equation.  A paradigm shift is required of all existing rebreather divers.  Speaking up when behaviors are witnessed that clearly deviate from safe practices needs to be standard operating procedure.  Terrence rightfully pointed out that we can go to a system based operation, but that is not going to be very pleasant for those that want to be able to dive without controls and support staff.

So, how do you shift to a new “good” cultural bias?  It is a difficult question and there is no easy answer.  Jill believes that checklist use needs to become the cool thing to do.  She believes that the role models in the sport need to drive that effort.  In some ways the changes in behavior can be easy, if it is established in the new users if that new user group explodes in number of users.  Much like a generational shift, not many remember not having CDs and many younger people have no concept of music being anything but a digital file.  The problem is if it does not change for them, then you are left trying to correct behavior already established in a much larger group of users than before.  So, the time is critical for this effort.

There was an assumption that training is taken care of by the audience, that there is little work to be done there.  In the last Forum, it was a critical question.  Advances in rebreather design may make the challenges easier to deal with, but the glaring lack of questions regarding the area of training should be considered when looking forward.

Is it safe to assume that training is adequate and not deserving of close evaluation?  Does the condition of training currently available in the industry warrant this belief?  Even with new developments, is training covering the necessary topics and providing the discipline and skills necessary no matter what the engineering requires of the diver?  Is instructor quality still or even more bound to good student outcomes than before?  Can a massive increase in users be safely handled if the instructor still matters far more than the program being used to train the diver with?  What should be done about it if this is all true?

Dr. Simon Mitchell moderated the closing session that reviewed the key points of the Forum.  Consensus recommendations were presented and voted on.  Not an easy task.  However, the work was far less conflicted than at the last Forum.  These recommendations are available on the Rubicon Foundation site.

Drew Richardson summed up the event, “After over 2 years of planning, RB 3 was a tremendous success and a worthwhile build on the previous Forum. The industry grows together when we work together and this is an example. The findings and interactions at this safety conference will help us move forward with closed circuit technology in a responsible manner”

Michael Menduno, the organizer of the first two rebreather forums, said, “I believe that rebreather technology is at another inflection point in its development. The first coincided with the emergence of technical diving—what you might call the “mix revolution,” which represented necessary infrastructure for the development of rebreathers. At that point, rebreathers like Bill Stone’s Cis-Lunar Mk-1 were just a tech diver’s dream. The second inflection point was in the mid-90s, with the emergence of the first sport diving rebreathers like Ambient Pressure’s Inspiration and the Dräger Atlantis.

Today, rebreathers are moving out of the “test pilot” era to become a true consumer product (think Poseidon’s Mk-VI or the Hollis Explorer). Granted, this transition will take time. Ten years from now, fifteen years from now, I suspect people will look back on today’s technology, and say “Geez, you actually dived those units without knowing exactly what you were breathing? OMG!” It’ll be like us looking at early cave divers using J-values and empty Clorox bottles for buoyancy, and going, Really?”