So, this stuff isn't supposed to happen, but I guess it does

[Redshift]

Nope.. A diver 'A' (the air hog) uses 1/3 for the dive, 1/3 to get back and 1/3 for emergency. The diver 'B' (the buddy) has always 1/3 of the air of diver 'A', but because he/she breathes better than 'A', then that 2/3 is enough for both of them. Basically the idea is for the 'B' buddy to carry more air for 'A'. If 'A' gets bigger tank, then 'B' gets even bigger. It's just 'B' will end the dive with extra air. That's all.

You are right, I wasn't considering he would always be the one with highest SAC (hence I deleted my previous post). But he'll get into trouble if it happens that he's not. So there are other ways to plan.

And that works with equal size cylinders, he doesn't need a smaller one. And he'll have more dive time also that way, while keeping a safe reserve. Although it still doesn't give him the same dive time as his buddies, which is what he'd like to have.
Of course, having a larger cylinder, as you say, may be a bad decision.
But, as DevonDiver said, we are talking about recreational dives. Usually there is no need for 1/3 going in, 1/3 getting back. In an emergency, divers are supposed to be able to ascend directly to the surface, so the needed air will be much smaller than 1/3. That's valid though in special circumstances where it's desirable to get to the same point.

 

[mrdre]

DevonDiver, points are well taken.

 

[PhatD1ver]

Since I am the trouble maker started this mess, let me weigh back in here, with the caveat that I do appreciate the pearls of wisdom and experience.

I do understand of the risks and the realities of running out of gas (both underwater and in the air).. .if you've ever landed a helicopter on auto-rotation, it will cause an emergency ascent from 30fsw to pale in comparison... I'm pretty sure that most people can go 10/10 with a 10m emergency ascent.... but you only get ONE shot at an autorotation without power...

Now, all the bravado aside... I'm not in agreement that I shouldn't carry more air while I learn to consume it more slowly. Everyone assures me that this will happen 'with time'...

In the meantime, let me ask a question for those that think a bigger tank with more available air is somehow wrong or somehow unsafe. Is it fair to the people who travel and dive with me for me to be the cause of curtailing their dives by 20-30 minutes? not just one dive, but EVERY dive while I learn to breath, relax, and smooth out my actions underwater? I'm a big guy, built like a freaking rhino (or hippo if your prefer)... I can swap up and handle the extra weight (and benefits) of a steel 90 or 100 very easily (and in fact, I used a steel90 in Thailand doing my OW)... at the same time, a steel 100 then offers me at my current SAC about 50-55 minutes of bottom time, which also coordinates with my DCL and the bottom time most of they people I am traveling and diving with...

So, as a 'responsible' and 'courteous' diver, isn't it MY problem to resolve? And if it means I have to carry a slightly higher capacity cylyinder, and recheck my weighting, I fail to see what is wrong with that? I'm still going to have to plan by 1/3s, I am not learning any bad habits, I still am going to have to plan to ascend and begin my safety stop by 70bar, that puts me on the surface with a reserve of 50bar in the tank. admittedly, it won't be a perfect 1/3 rule. But it is responsible planning. And my buddies air is still there for THEM, and I still have air for me... just like we are taught in OW training... show where is the 'bad habit transfer?'

I've never seen anywhere in what I've been taught that I am supposed to force other divers to match the limits of my SAC without any adjustments to my equipment. For you more experienced types, I'd wager you wouldn't continue diving with me if you were forced to do so.

As I learn to breath more efficiently and get fitter and lose some weight, the blessing will be first dumping weights, then being able to enjoy diving deeper for longer (within my DCL)... and that then means I can make use of EAN more economically (since for my age, the NDCL dive profile is significantly wider where I can enjoy EAN benefits), but only if I'm not if I'm chewing thru it in 25 minutes total bottom time.

And it's courteous planning so that my dive partners can get the most enjoyment for their money on trips that can cost hundreds, if not $1000s of dollars. Rather than curtail their dives by 20-30 minutes (or more for some).

As far as my idea for using a pony tank, that topic also seems divisive for some reason, and I guess someone needs to educate me on how carrying 30cf extra in a pony bottle is any different than simply carrying a larger capacity primary air cylinder. Other than the task management for knowing when to go to the pony and then back to the primary what difference does it really matter where you carry the extra air? Especially when your dive location only has small capacity cylinders available?

So, I guess I'm in for a beating, but I'm still all ears here.

---------- Post added July 14th, 2014 at 11:22 AM ----------

unless your SPG is in a very unconventional spot it should be easy to monitor it, you just need to keep that in mind at all times and check it, especially when you know you're using air fast, overdoit at first if that's what it takes to get you into the habit, afterall your air is one of the most important parts of your safety underwater
i made a habbit if checking mine quite frequently at the begining of the dive just to make sure there are no issues, sure they can arise further into the dive but if at all possible why not deal with it at the beginning?

can also plan to do your safety stop while you still look around in the shallows, there's lots of pretty stuff there too

Yeah, the SPG problem is that I have a large obstacle right now below my chest and just above my waist, called my protuberance (fat stomach)... so my SPG kind of hides down there on my left side if I don't place it right on top of the 'table' so to speak... I've found that it's easier to do that way, and easier to focus too and see my markings...

---------- Post added July 14th, 2014 at 11:41 AM ----------

PhatD1ver, thanks for posting this. Sometimes when people are brave enough to post examples of their mistakes, some of the regular users here can be very sharp in their criticism and the OP gets offended and never returns. So far, the replies to your post have been quite gentle compare to what I've seen here. (That or the moderator has already been busy! ;-) One of the things that improved my SAC rate and diving enjoyment was getting in better shape.

no worries, I'm pretty thick skinned, and I've learned the way to learn from my mistakes is to admit them and then see what others say about it... there will always be the ones that want to criticize rather than critique, and the ones that believe they have the only solution.

One of the things to keep in mind was that this happened with my instructor right there, he was the guy who had to share air, so you can be sure that he made some on the spot corrections both for me, and for himself, and the other 9 dives went off without a problem. I was never in any danger, I've been over my dive profile from that dive, and at the end, I was capable of an emergency ascent at any point without any likely risk of DCS (especially given this was my first dive, not dive 10).

So, again, I'm not trying to minimize the problem, I'm trying to find effective solutions that allow me to manage it better. The things I've learned since that dive are:

1) better situational awareness (I use my spare watch attached to my BCD as a safety alarm, it's set to go off at 3 minutes on a repeat alarm, worked like a charm)
2) back to working on fitness (this is tough, I already swim 2-3 times a week, and run/jog 2-3 times, and I love to eat, so it's a work in progress)
3) pack more air - sorry folks, command decision is that in the short term, I'm going to carry more air, starting with a steel 100. for the added capacity, versus negative buoyancy (which I already need), it's a win win.
4) get more dives in, relax and enjoy diving without too much more 'training' (that tends to stress me a little more than just getting wet).

 

[doctormike]

In the meantime, let me ask a question for those that think a bigger tank with more available air is somehow wrong or somehow unsafe. Is it fair to the people who travel and dive with me for me to be the cause of curtailing their dives by 20-30 minutes? not just one dive, but EVERY dive while I learn to breath, relax, and smooth out my actions underwater? I'm a big guy, built like a freaking rhino (or hippo if your prefer)...

As far as my idea for using a pony tank, that topic also seems divisive for some reason, and I guess someone needs to educate me on how carrying 30cf extra in a pony bottle is any different than simply carrying a larger capacity primary air cylinder. Other than the task management for knowing when to go to the pony and then back to the primary what difference does it really matter where you carry the extra air? Especially when your dive location only has small capacity cylinders available?

First of all, it makes no sense that anyone should object to you using a larger tank. It's pretty common for buddies with mismatched SAC rates to have different primary tank volumes. Yes, if you are diving in an overhead environment, this does involve some math if you want to do gas matching, but all it means is that your planning has to take into account the different SAC rates, starting pressures, and starting volumes. But that's not really the issue with your diving, all you and your buddy need in terms of an emergency shared gas volume is enough to cover your immediate ascent to the surface using one tank (in case of catastrophic gas loss), which is not so onerous.

Secondly, as one of the ones who vehemently objected to your using a pony as part of your gas planning, I have had second thoughts. What you are describing is not a pony bottle but a stage bottle, and while that's not typically something carried by new divers, I guess the main objection would be (1) the task loading of switching regulators and (2) the risk that if there is a problem with the pony and you have drained your back gas, planning to finish the dive on the pony, then you will be once again OOG.

So if you were to (1) descend using your back gas (to make sure that system is working), (2) use the pony first and (3) when it was low switch back to your back gas, you wouldn't be incurring that much more risk. However, your dive plan now has lost all redundancy, and your survival now depends on both regulators working during the dive, or finding a buddy for that emergency ascent if you drain the pony and then find your back gas regulator is no longer functioning.

So, still.... not the best option. The best option would be for you to carry a tank appropriate for your SAC now (even as you work on improving it), AND to carry the pony for redundancy (not including it in your gas planning). But maybe one less "NO" than I previously posted...

 

[lemke]

Interesting points by all, and, as some eluded to, your air consumption will decrease with time and experience. One simple exercise to control your breathing is to exhale for twice as long as it takes you to inhale... it becomes second nature after awhile and really helps keep you calm.

 

[doctormike]

Interesting points by all, and, as some eluded to, your air consumption will decrease with time and experience. One simple exercise to control your breathing is to exhale for twice as long as it takes you to inhale... it becomes second nature after awhile and really helps keep you calm.

Absolutely true, but also any new divers reading the thread should remember, the OP had nothing to do with SAC rate. The requirements for situational awareness and gas planning are exactly the same whether you have a SAC of 0.3 or 1.1.

 

[MXGratefulDiver]

1. NO! DO NOT get a bigger tank. It's a big mistake many make. At first it sounds intuitive: "well, you use more air - get a bigger air supply". NO! it's wrong. If you use more air, actually, you will need a SMALLER tank. Why? Because your buddies are planning based on THEIR consumption rates. In case you have a catastrophic tank failure, your buddy will share his air with you, planned for HIS consumption rate. You will breath your buddy's air out very fast leaving both of you out of air. You need a smaller tank, so once you are out of air, then your buddy's tanks will be enough for safe return to the surface.

That's dreadful advice. You shouldn't PLAN to run out of air ... and then count on your buddy to have plenty left for both of you. That's dumb. What if your buddy has a problem that requires the two of you to use your supply? Will you have enough to get both of you to the surface safely? If you're the higher consumer with a smaller tank, it's doubtful that you will.

If the option's there, giving a high-consumer a bigger tank is NOT a mistake ... it's the sensible thing to do. Considering what to do if you should go OOA is all well and good ... but taking steps not to go OOA in the first place is a way better plan.

2. The only solution for you - is to practice. There is no such thing as "I consume a lot of air and that's it". No. It's a skill too, and it's really not that hard. First, practice "yoga breathing" - use your diaphragm. Practice every day, take 10-15 minutes for that. Underwater do yoga breathing. Inhale slowly, exhale even slower. Experienced divers can exhale for about 40 seconds.

I'll agree with the first sentence ... the rest of it, not so much. Yes, proper breathing underwater is an acquired skill. Much of it comes from developing your basic diving skills to the point where they don't require much effort ... which comes from proper trim and buoyancy control, and from just diving. The problem with trying to teach people to change their breathing pattern is that there's a high potential for CO2 retention, which not only won't reduce your gas consumption but can have a range of ill effects for the diver. For some, practicing "yoga breathing" can be helpful ... for most, the potential for doing it wrong and therefore building up the CO2 levels in your body is high and will lead to stress as you struggle with that "I can't get enough air" feeling. Underwater, stress is not your friend. A better approach for most people is to work on your basic physical diving skills while breathing normally ... over time, as you acquire more comfort with what you're doing, your air consumption rate will self-correct.

3. Practice finning, improve your trim. You will use much less energy and much less oxygen will be required.

While you're correct about the finning and trim advice, oxygen use isn't what causes newer divers to breathe so much ... buildup of CO2 in your body is. But that wasn't really what caused this diver's problem ... lack of maintaining an awareness of the amount of air remaining in his tank was. In this case, that's really the skill that's in most immediate need of attention ... learning to pay attention to what's going on while you're focused on the more immediate concerns of the dive. It's one of the most important skills a diver can develop ... and one that's not very well emphasized in most basic OW classes.

4. In the scenario like this, I wouldn't swim against the current if I feel overexerted. I'd just do a surface swim. Once I had to swim on the surface for 3 hours against the current. Not that hard.

It depends ... it's not uncommon for surface currents to be stronger than currents down 10 to 20 feet below the surface. Depends on a number of factors, including (among other things) the direction of the wind, tidal conditions, and topography. There are many places in the world where swimming against the current on the surface isn't only ill-advised, but virtually impossible ... particularly if you're diving in a place where there's a lot of kelp.

Some other comments to direct at the OP. First ... don't get so caught up on the safety stop that you run yourself out of air. Get your priorities straight ... as long as you're within no-deco limits, a safety stop is precautionary and optional ... breathing is not, and therefore once you realized you were OOA, your priority should have been to get to the surface. If your choice is to run yourself out of air while doing a safety stop vs surfacing early while you still have air in your tank, go to the surface. The worst-case risk (DCS) in the latter case is fixable ... the worst-case risk (drowning) in the former is not! Secondly, don't rely on a DM to make your decisions or to get you out of trouble ... they're not there to take care of you, and they won't always be able to. If you realize you're so low on air that you need to surface, signal them you need to go up. That thumb isn't a request ... it's called a command signal for a reason. If they try to overrule you, go up anyway ... only one person's responsible for your safety, and that's you. Take charge of your decisions ... your life depends on them.

... Bob (Grateful Diver)

 

[flots am]

In the meantime, let me ask a question for those that think a bigger tank with more available air is somehow wrong or somehow unsafe

There's absolutely nothing wrong with bigger tanks. I bought four of them when I first started diving, because I didn't like to be the guy that always cut everybody else's dive short.

The only "problem" is that they don't help when you're on vacation. Other than that, buy whatever you want and enjoy your dive.

As far as your SAC rate goes, you can't directly reduce it. The only way to use less air is to do less stuff that uses air.

If you can reduce your energy consumption by being weighted properly, maintaining proper horizontal trim, moving slowly, relaxing, and staying out of the current, you will then use less air.

You can't simply "use less air" by "breathing less" anymore than you can improve your car's gas mileage by crimping the gas line. Use less energy and you'll use less air.

flots

PS. I'd skip doubles until you're been diving for a while, and even then, you should decide if you want manifolded doubles or side-mount. Manifolded doubles require that you be able to quickly manipulate valves that are behind you, which is not something everybody can or wants to do.

 

[tech_diver]

Thanks to the OP for posting. A couple of random thoughts on the thread...

Don't worry about being bashed on the forums. Even if you've been a diver all your life and spent decades in the dive industry, people will still bash. Even if it's just over a 15 year old photo of you with your octo hanging a little low.

A larger tank can be an answer but it has to be a realistic answer that doesn't add task loading. New divers sometimes think that double tanks will double their air time and they fail to consider that double tanks can also increase your SAC rate by 20 - 30 percent. A bigger tank can be a practical answer, just be sure to do the arithmetic (with your SAC) to make sure it's a positive answer.

Also, you will be very surprised how much better your air consumption will increase by virtue of experience alone. There are big beefy DMs doing 4 dives a day who (on a single tank) can outlast a slender jogger that only dives on vacation. Freedivers will tell you that much of the air consumption game is mental.

 

[TSandM]

I see no reason at all why the OP shouldn't have a bigger tank. My husband and I don't dive the same tanks; he has a higher SAC rate than mine, so he dives 130s to my 100s. Where we CAN do this, we always do. As long as everybody maintains the agreed-upon rock bottom reserves, why does it matter how much extra gas you have along? If you turn around when you hit half your usable gas, does it really matter who did the turning?

To the OP -- I appreciate your desire not to discommode your companions. A big single tank is a great idea. Carrying a stage may really not be -- if you are having situational awareness problems monitoring a single tank, this will be compounded with two. You will have two primary regulators, and will need to keep track of which one you are using, so you know which volume to track. If you get confused and run a tank dry without realizing it's happening, will you be able to remain calm and switch to the other? Do you have a rational gas management plan for which tank to use first? Do you know what will happen to your buoyancy if you run one tank empty?

New divers are bandwidth-challenged, which is why they get into trouble like you describe in your first post. Making their equipment more complicated isn't the answer. The answer is improving situational awareness. Try setting yourself goals, like checking your pressure every five minutes without fail, but estimating to yourself what the gauge will read BEFORE you look at it. You'd be surprised how fast you learn to be good at that . . . which means that, as you watch the time click off on your computer, you will have a good visceral sense of where you likely are on gas.

I was having lunch with a friend who is a GUE instructor yesterday. We were talking about diving fatalities in our respective corners of the world. We both agreed that new divers go out terrified of DCS, which they almost certainly will never have and probably will never see, and not NEARLY worried enough about making sure they maintain adequate reserves of gas. That's getting priorities bass-ackwards to me!