When does "Gas Management" get taught?

[limeyx]

Yes, but I have serious doubts that standard AOW-trained divers will only spend a 1 minute at depth before ascending in an emergency as well. Our RecTriox class highlighted how terribly insufficient (or non-existant) the training was in standard scuba classes to just get off of the bottom as fast as you can. For example, 3 mins at 100 fsw + 3 min 30 fpm ascent at a 1.5 combined SAC rate is 13.5 cu ft + 8.40 cu ft = 21.90 cu ft which is 900 psi.

Yup, I've seen upward of 10 divers clinging onto kelp (luckily only at 40 or so feet) in a raging current looking for the anchor line (which had skipped and moved). Some of them breathed their tanks right down to zero rather than ascend!

But that I guess is a whole different conversation.

 

[limeyx]

While I agree that diving thirds in OW is strange, I do want to comment on a few points.
Your buddy breathing more than you doesn't cause a problem with diving thirds. If he breathes more, then he reaches his turn pressure early and you turn the dive (and you have a crap load of gas left because you never even reached your turn pressure). If your buddy breathes more than you and you reach your turn pressure, your buddy is not a buddy because he has dipped into your third in his tanks. And of course, this all assumes proper 'gas matching' was done. Diving thirds without gas matching is pointless (not that you were suggesting otherwise).


I was taught that calculations were made once in the water to allow your tanks to cool (or heat as they do in cave country in the winter months ) which will change your pressure.

Fair points, if you do proper gas matching on the 1/3's -- however, I'm not convinced people necessarily learn thirds that way in all cases. It seems more likely that they just calculate 1/3 of each persons gas and leave it at that. If the slower breathing person has smaller tanks, then you have to do 1/3's on the least gas so that the heaviest breather can get back out on it.

and yes, agreed on checking pressure in the water as I can make a difference, but you ought to have a good feeling for the numbers before you hit the water. Then you can make an adjustment based on any cooling I would say.

 

[limeyx]

Sadly, "exit the water with 300-600 psi or more if the dive conditions warrant an extra margin of conservatism" is perceived by many as "gas planning."

It's a good thing all open water recreational divers dive the size tanks and all dive the same profiles. Or do we?:headscrat

well, it's a fine rule in that if you can get back to the boat/shore in any conditions (OOA, lost buddy etc.) with 3-600 psi

It's a lame rule because it tells you *what* to do without giving you any clue of *how* to acheive such a thing.

 

[cerich]

That S & P stuff you quote is the simple stuff that everyone teaches ... monitor your gauge, signal pressure upon request, and surface with 500 psi.

That's not what I mean when I talk about gas management ... there's more to driving than learning how to turn the steering wheel.

I teach my AOW students the concepts behind surface air consumption, how it applies in the context of depth (Boyle's Law and all that rot), how to convert between psi and volume (cubic feet), how to determine turn pressure relative to your dive profile, how to determine rock bottom pressure, how to calculate the amount of gas you'll need for a given dive plan, techniques for good gas management habits, and tips for better gas consumption. Prior to the deep dive we measure gas consumption at depth, convert it to SAC and RMV, and use those figures to calculate gas consumption for the deep dive based on a written dive plan.

I don't train "vacation divers" ... up here there are no DM's to follow around ... not even on the charter boats. Once you're certified, you're pretty much on your own. I want my students to be able to dive responsibly ... and that means knowing how to NOT run low on gas at depth.

AOW is, to me, a generic term ... I use it here because it's generally understood by divers of all agencies.

... Bob (Grateful Diver)

It's only the simple stuff it you make it that way. I teach what you describe for your advanced course in the scuba diver course. 90% of what you listed is "must teach" stuff anyhow.

Bob, I've taught in Nova Scotia and the Great Lakes in Canada and the carib. the location does affect the course but doesn't have to an effect on the quality unless one allows it to as the instructor. I'm not busting your chops here.

This whole post bothers me, this stuff should be and needs to be taught, regardless of the agency. The idea that some have that DIR fundies are the way to get training in basics is wrong, there are instrs. for every agency that do a great job of covering what a diver needs to know and instrs. for every agency that shouldn't be teaching..

As instructors we need to always ask ourself if we are doing our job right.

Best,

Chris

 

[TSandM]

Well, the thread was started by my husband, who has gone through training with our original agency through rescue and the only place he had heard about gas management was from me, because of my exposure to Bob and to GUE. I think it should be taught -- or at least more of it should be taught -- at the very least when you start doing the deep dives (and both my husband and I did the deep specialty, with three dives, and there was no discussion of a "rock bottom"-like concept except when I brought it up). It's not in the written materials, which suggests that it will only be taught by individual instructors who have decided to add it in. That just seems regrettable.

 

[Jason B]

Fair points, if you do proper gas matching on the 1/3's -- however, I'm not convinced people necessarily learn thirds that way in all cases.

From the looks of this thread I think your right (unfortunately).

It seems more likely that they just calculate 1/3 of each persons gas and leave it at that. If the slower breathing person has smaller tanks, then you have to do 1/3's on the least gas so that the heaviest breather can get back out on it.

And this is what you were getting at in the post I referenced early. I gotcha now. Misunderstanding. We are in agreement 100%.

 

[paolov]

well, it's a fine rule in that if you can get back to the boat/shore in any conditions (OOA, lost buddy etc.) with 3-600 psi

It's a lame rule because it tells you *what* to do without giving you any clue of *how* to acheive such a thing.

that i believe is the instructors role. i inject the *how* at PPB classes.

.

 

[cummings66]

I was taught basic gas management in my Padi OW class, but for what most people would consider gas management I'd tell you that my NASE AOW class taught me about it in detail. I.e. you went out and discovered your various breathing rates and then learned the math to do the actual numbers for a dive. In other words you planned the dive based on how much air you would use at depth and also how much air your buddy would use of yours as well, and in that class I learned that the basic gas management I learned in OW was not very useful. You can be on the surface with 500 psi easy enough, but does that account for your buddy? Does it take into consideration anything beyond start coming up before you hit it? Not really.

 

[limeyx]

that i believe is the instructors role. i inject the *how* at PPB classes.

.

And I think it's great that you do that. However, it doesn't seem to be "required" (or if it is, it seems to get overlooked somehow), and doesn't seem to actually end up being taught very much.

Also, as Jason pointed out, it does take a while to sink in (I am cringing remembering back at our first lame attempts to calculate simple minimum gas), which is why it's best to start as soon as possible, so that people have more time to really appreciate how to do the calculations.

 

[lamont]

But the question was is 800 psi going to get two divers to the surface safely given 1 minute for emergency and 30' per minute ascent. I'd say yes under those circumstances.

And I don't believe that is the question. I think the question is "how much gas do AOW divers need to reserve at 100 fsw in order to get back to the boat safely?" In assuming that they'll spend a minute at depth and blow off their safety stop you've already assumed an awful lot.

And the running joke in my RecTriox class was that "West Coast DIR" is using double E8-130s because we factor in 15 mins of time at depth to sort out the problem...

Sherwood was a little incredulous at first that everyone was wearing double 130s for 100 fsw weenie dives, but after he saw us in the water he started to understand... =)