Rebreather Pro: Lamar Hires on CCR Risk Assessment

  Technical diving pioneer and Dive Rite CEO Lamar Hires

Risk Assessment for CCR diving
My specialty is cave diving so I look at risk factors based on the cave environment.  Divers refer to the overhead or ceiling as anything that prevents a direct ascent to the surface. For many divers this is the decompression after a deep wreck dive.  For me it’s about the trip home, the cave entrance. Failures in a cave still require an exit before worrying about decompression, so bailout and gas management are calculated differently.  We need to carry bailout for the exit, based on penetration, flow, visibility and hazards (restrictions). This is typically more bailout then wreck divers since their concerns are ascent and decompression. In caves we can stage bottles and decompression gas so we don’t think about what we can carry, but rather where to stage it.
How much bailout is enough or when is it overkill? (Click below to continue)

Risk assessment is a personal perception and acceptance of the risk-to-reward of a dive plan. Some look at the minimalistic approach while others want to make sure that every contingency is planned for. Example – Cocklebiddy Cave in Australia was explored by the Aussies using sleds to carry an abundance of gas to push the cave beyond Toad Hall. A Frenchman came in with a minimalistic approach using scooters and pushed the end of the known cave with a small team on one dive, (camping at Toad Hall); a different approach and different perspective of risk-to-reward.
We all have a different perspective of risk-to-reward and we need to be aware of setting parameters based on one’s own standards. Some of the factors may be health, physical fitness, familiarity with a dive site, skill level and dive partners. We all approach risk differently and can look to other sports and activities when we make evaluations.  Do you drive the speed limit or push it to the limit of safety or what you think is allowable without getting a ticket? Snow skiing is a good parallel: the trails are rated with level of difficulty, green for novices, blue for intermediate and black diamonds are for experts.  You can take lessons to increase your skill level before venturing on to more difficult trails, but you always have to weigh the risk-to-reward when you venture on to more difficult trails. Just like CCR diving you need to weigh the risk-to-reward factors.
I hope by now you have a grasp of my risk-to-reward concept.  The following is my opinion on risk-to-reward for CCR cave divers.  The amount of bailout a diver should carry for a dive seems to be the topic of discussion. What is an adequate amount of bailout for a diver? Should a dive be planned on a team concept or on individual self rescue concepts? I have to answer “it depends,” but on what?
First let’s define bailout – “The gas needed to exit the cave in the event of a total loop failure“.  Divers practice and execute exits during class to affirm this, but a drill is not the real thing. During a drill all events are controlled; even if the events are spontaneous it is still just a drill. Many assumptions are made during drills and there is always the peace of mind that it is just a drill. Breathing rates are controlled because it is just a drill (you can go back on the loop if you need gas), we need to factor in the “oh sh#?t” factor to see what happens to breathing rates and bailout needs for an exit.  How much gas is expended before you determine the loop is “toast”? Now reality sets in on a number of levels.  1)  How long to get out? 2) How much gas do I have after trying to solve the problem to get back on the loop? 3) Did I stage enough deco gas for this scenario? 4) How fast can I get out (further elevating the breathing rate)?
Risk-to-reward evaluation
As a cave diver I believe in redundancy. If I am down one regulator then I have serious problems and I need to get out of the overhead situation. This does not sit well with me. I can’t shake the cave diver mentality. There is safety in numbers or redundancy as we cave divers refer to it, so I will not set bailout up on a one bottle scenario. My choice is to carry two bailout bottles in a sidemount configuration for streamlining and balance out the gas. If I need 80 cu ft of gas, which is common for most dives above 130 feet, then I carry two 40 cu ft cylinders. If the dive is deep or long requiring more bailout then I carry two aluminum 80 cu ft cylinders and/or stage the gas considering variables like flow, restrictions, DPV and visibility.
I find there are open circuit divers that try to impose their perspective of risk-to-reward on CCR divers, yet don’t follow the same rules. For instance, the average cave fill is 300+ cubic feet of gas, but a solo cave diver is happy with a single aluminum 80 for bailout. Do the math; this is not 1/3 of the starting gas volume so how can 80 cubic feet be acceptable for open circuit divers when they need to carry at least 100 cubic feet? The answer is comfort level. Open circuit divers are comfortable with an aluminum 80. It is perceived as enough volume to take care of any problem. If a diver has to use this bailout bottle then he is down to one regulator and serious problems for the trip home, but the odds of using it are so slim that the risk is acceptable to most cave divers.
CCR divers don’t have this long history to fall back on. We use open circuit procedures as guidelines to develop our own risk-to-reward assessment.  As I push farther into the caves on CCR, I weigh and re-weigh the risk-to-reward element. What works for me today may not be right for tomorrow. I started with a single bailout bottle, sometimes a 40 cubic foot cylinder in a team management plan and then an 80 for longer dives. Today, I dive twin 40 cu ft bottles for an average dive of 1500 to 2000 ft penetrations on dives averaging 100 ft in depth, then move up to twin 80’s and stages for deeper or longer dives. Sometimes when the cave is small I use twin 40’s and 80 stages like diving at Rose. My last big dive in Devil’s Ear was a 4000’ working dive so it called for twin 80’s bailout. Bailout style is determined by the mission, a single dive site may require multiple bailout configurations based on the objectives.
Bailout management plans – The team concept or self sufficient. This appears to be the argument today.   As I stated earlier what I carry is a mission based plan.  I have already heard the comment that a recreational dive for me may be a push the limits dive for another diver, so is the difference in bailout requirements.  Traveling the main line in a popular cave system, doing a dive I have done before on OC is very different from planning a push dive. On the recreational dives the team concept works very well, I carry the feel good 80 cu ft of gas but in two aluminum 40 cu ft cylinders.  I am self sufficient for bailout but able to help a buddy in distress since my bailout is in two cylinders.  On longer dives both methods are used.  We stage gas in for bailout but since we aren’t breathing it we stagger the bottles to give either team member as much gas as possible in the event of a total loop failure.  For instance on a 4000’ push at 130’ we drop a bottle at 1400’ (best location for visibility) another at 2400’ and then we drop DPV and swim on with 80 cu ft each  (in  40 cu ft bottles) because the cave gets small and we need wiggle room.  If it was a three man team there would be one more 80 cu ft bottle dropped to leave a nice trail out gas for the team.  On long DPV dives with no swimming involved we would just carry 2 aluminum 80 cu ft cylinders each.
I gauge my bailout needs on my open circuit experience for exiting a cave and plan accordingly.  I suggest that CCR divers look to open circuit gas management and use their reserves as a meter for bailout needs. If an open circuit diver is going to do the dive on a set of high volume doubles, then a couple of 40 cu ft cylinders should be adequate bailout for a CCR diver. A CCR diver has more options when problems occur; switching to open circuit bailout is often the last resort.  Planning is critical, but understanding ones needs is very important to planning. Do not plan a dive on best case scenario, but rather a realistic worst case scenario. --LaMar Hires