Bailout gas.....how much is enough?

[matt t.]

I will start this out saying that I am NOT a CCR diver. I do dive regularily with several CCR divers that dive several different units, and I am familiar with their features and what to do in case of trouble. For the most part I agree with the mixes and amounts of bailout gas they carry (obviously they will vary depending on the dive). I'm curious how other CCR divers are planning their bailout scenarios as far as gas amounts and mixes. What I'm seeing 1st hand and reading on dive reports is that the majority of CCR divers don't carry enough bailout gas. I don't believe in "team" bailout gas do to the nature of the bigger dives being done and the need to be mostly self sufficient. I'd like to hear from some CCR divers and what they might take along as bailout (and even diluent) on a given dive. Discuss...

[systematic.entropy]

Easy. Enough gas to get YOU to the surface safely  ;D. I don't follow the Tom Mount "Team Bailout" method. That being said, if I'm in a cave, and know, that I can make it out from 1000ft on an AL80 (given SAC rate, experience with the system, etc.), an AL80 is my bailout. My buddy will be doing the same, so, even if all my bailout regs malfunction, bottle blows up, I'm held up at gunpoint, etc., I still have his bailout to fall back on for 100% safety. Also, in such a situation, it'd be prudent to have an AL40 of O2 waiting at my deco spot. Two bottles, buddy redundancy, not dependence, all bases covered.

Usually for recreational depth dives on the Lake, I'll carry an AL40. If something goes wrong on the dive, and I have to bailout, that's more than enough to satisfy any of the minimal deco I may have, and get me to the surface. Also, please remember many, many, many problems that cause divers to "bailout" can be solved, and don't necessarily constitute staying off the loop. Often times a few seconds on OC will be enough to identify a loose fitting, isolate a blown o-ring, etc., and one can go back on the unit for required deco, travel, etc.

Also, I have not yet been doing any heavy deco or trimix CCR diving. I have no experienced opinion on those logistics.

Good thread.
However, I will completely agree that many CCR divers I've SEEN (of course no one I personally know and dive with), do not dive with enough bailout. I mean, seeing someone go into a cave on a YBOD with a single 40, gives me the heebie jeebies.

[Scubaal]

If you have ideco on iphone its fun to play with the different "what ifs" Really eye opening as to bailout mixes and size of bottles. As a person dives past 200ft. Two bailout mixes seem to work out much better when it comes to getting the diver out of the water.

From Ideco: 225ft/20min 10/50 trimix w/1.3 set point. Total runtime 67min.
Bailout using 21/35 and 100% O2 total runtime 96min. 124cf of 21/35 and 24cf of O2
Bailout using 21/35, 36% and 100% total runtime 67 min. 60.5cf of 21/35, 33.7cf of 36% and 18cf of O2

So for our deeper dives we are starting to carry 1-80cf and 1-40cf of mix along with a third 30 or 40 of 100%. In some stiutations 2 40's instead of the 40&80

We have moved away from the 1 1/2 gas need carried by the team (2 divers) to carrying 100% of the individuals needs.

Al

[sum-yung guy]

Having no CCR experience at all but quite a bit of OC under my belt, I feel that in any situation having more than enough gas to get to the surface in a problem is always a good thing. As I move into CCR in the next few months, I am going into it with the mindset that I will always be carrying enough gas to get myself to the surface in any type of situation comfortably and with gas if my buddy has issues. I have heard about many CCR divers who dive the team philosophy, and personally can't find my "warm fuzzy" feeling to think about diving it. I have always been taught in the technical realm to dive with enough gas to get yourself to the surface and (on the rule of 1/3's) your buddy too. I practice this style of diving to keep not only myself comfortable with ever having a problem at depth, but my buddy too.

I understand that some people move to CCR to minimize the amount of gear they are carrying, but at what cost do you not carry enough gas to save yourself?  ??? I can see if you are using a rebreather recreationally without a huge amount of deco and could bail out to OC to get yourself to the surface and any minor stops you might incur. But for any big dives, I always come back to the question...why wouldn't you carry enough gas for yourself?

Lets be honest...the chances of everybody having a major problem at the same time are minimal, but why leave that to chance? Don't we train for the worst case scenario for everything? Even starting at Open Water with our five different ascents that we teach. We will never get to the last one if we follow the first four steps before it, of course the first being, don't run out of air!!!

If we go back to our bread and butter of diving, it seems to make sense to me, but everyone learns a different way and that is why I am always open to hear about everyones different styles of diving to learn more about diving in general.

Good Thread, I am curious to see all the different responses!

[deep_al]

First of all I believe in always carrying all of my bailout, not because I think team bailout is majorly flawed, but because I dont have a ccr buddy that I dive with enough to make team bailout a legitimate plan. 

Team bailout isnt for the average dive though, its for the dives that require it.  Carrying 2 80s is no problem, especially since, without a 7ft hose, you can sling bottles on both side (right=rich, left=lean).  The issue arises when you enter a situation where your using your rebreather to its full potential.  Plan a 20-25 min, 350+ft dive and figure the bailout requirements. Youll need at least 4 bottles, deep bailout, intermediate deco gas, another deco gas, and O2.  You need a good deal of your deep bailout to make up for your high breathing rate from the stressful situation, so you'll probably want an 80 of that, then you'll need a very full 80 of say 20/30 to get you up to your next gas, then you'll just about empty an 80 of 50%, and youll get out of the water with a nearly empty 80 of O2. 

Now Im not saying saying you cant carry 4 80s on a dive, but four 80's of bailout would get you out of the water by the skin of your teeth, remember that a CO2 issue or a total flood that would force you off the loop is going to effect your normal sac rate by quite a lot. This bailout is also assuming that you plan your bailout with the same deco you normally dive with.  You could use a really steep GF for your bailout tables that would get out out of the water a little quicker, but I would consider shortening your deco stops a last ditch effort. Ive been told: you can get un-bent, but not un-drowned.

In the end, RB's dont have that many failure modes that would require you to get off the loop.  Your bailout is your bailout, its your last ditch effort to get to the surface.  Its like a pilot and his parachute, hes not gonna jump out of the plane untill he knows there is no way its going to survive the landing.  Loop flushes, using off board gas, flying the unit manually (for you eCCR guys), and SCR are all ways to keep you on the loop and off of OC, because if you bailout and something else goes wrong where do you go then?

Theres no reason for a CCR diver to not carry enough bailout gas down to 250-300ft after that things could get a little stressful, without team bailout. 

There is a certain level of trust for, or better yet, understanding of your RB you need to develop in order to go into the major dives that require huge amounts of bailout.  As you practice diving your CCR you get to know how it acts, you learn about the cell readings and the sounds you should be hearing.  With a manual rebreather you even get a feeling for how the PO2 should change based on how long you add O2. 

For example, my cell #3 was always a little slow compared to the other 2, and I always kept an eye on it, last weekend it was reading really low in air (0.14) during calibration 100% O2 at 1atm it made 38 millivolts instead of the 48ish millivolts of the others. During the dive it read a little lower than the other two (about 0.15-0.2), and when I did an O2 flush at 20 feet it jumped to reading high (about 0.3 above the other two).  The point is that I expected that cell to fail me at some point, and I was ready for it. 

The point Im getting at is that you develop an understanding of your rebreather and that understanding lets you decide how you react to different failures.  If one of my other cells had suddenly read 0.3 high while I was at 200ft, my reaction would have been very different (dil flush, and evaluation), but I knew this was coming and I knew it wouldn't be something to worry about. 

That all being said Im still new at deep trimix dives and haven't gone to a depth where I feel uncomfortable carrying my own bailout.  But with the right teammate I have no problem dividing up my bailout for dives that require it. 

Sorry for the rant, but it is an interesting subject, especially the failure modes of rebreathers and the thought process behind completely bailing out to OC, since this significantly controls your thoughts of bailout supplies.

-Al

PS hey Mike what RB did you decide on? 'boris?

[Vtach]

I carry enough to get me to the surface, not a fan of team bailout at this point.  The only time I will dive a 40 is when I am shallow (100ft or less) and there is no decompression obligations.  So...it is pretty much at least one 80 for most dives.  Planned decompression dives, I will carry an 80 of bailout and an 80 of 50% up to 200ft.  Beyond that and I start adding more bottles....

I think a big point to make is that bailing early in a failure is paramount.  Once you choke on caustic or take a big CO2 hit, you will suck that bailout dry in no time and may find it difficult to reach a depth for the next gas switch.  If you are maintaining good situational awareness you can bail as soon as you recognize an issue arising.  You should still have your wits about you and may have the ability go back on the loop and manage the problem.  That is the nice thing about CCR, you have multiple options and if you are smart on how you use them you may not need your full bailout supply.