When does "Gas Management" get taught?

[lamont]

Eh? The standard recreational diving safety procedure is - if something goes wrong, you go up. Recreational diving is predicated upon the fact that the surface is 1-2 min away, regardless of where you are in most cases.

Vandit

The surface is only a minute or two away provided that you make the right decision to leave depth immediately when a problem occurs. A great deal of the in-water experience and training in RecTriox and Tech 1 is just instructors highlighting to students how divers will make mistakes in judgement about leaving depth (with video evidence of a plethora of mistakes made by students in the class), and to try to fix that and hammer into students that they need to drop what they're doing and leave when it starts hitting the fan. I definitely don't think that AOW students with 100 dives or less would be able to consistantly get off the bottom fast enough so that an "800 psi / 50 bar" rule would be sufficient for dives of 100 fsw. Even with blowing off stops, you need more gas than that at that depth, and I don't think blowing off stops at that depth is particularly a smart thing to be planning on, even in emergencies.

 

[Adobo]

I must have have missed something. What is this complex math that has people's feathers ruffled?

I was taught to use basic math to work out usable gas, turn pressure and rock bottom. While I did see the logic used to determine rock bottom, I still always use the rules of thumb to determine rock bottom (since I know and trust the math that was used to calculate it). Diving a steel hp 100 with max depth less than 100 feet? Here is your rock bottom. Diving an aluminum 80 with max depth less than 60 feet? Here is your rock bottom. Before the dive takes place, I know that if I am near my rock bottom when I make my ascent, I know what kind of ascent profile I can make and still have plenty of gas if during the ascent, my buddy runs out of gas. These are recreational diving profiles we are talking about right?

I could be wrong but I think one of the misperceptions here that gas planning involves complex decision making underwater. In fact, it seems to me that with gas planning, any complexity (what little there is) is tackled well before you show up at the dive site.

 

[rjack321]

For the vast majority of "real world" situations, the surface is indeed 1-2 min away, even assuming proper ascent rate. And even in the extreme case of someone being at 120-130 ft, and being completely OOA, and with a buddy who also happens to have only 50 bar in their tank (shall we throw in a few killer sharks as well, while we are generating a worst case scenario?), coming up a little faster than 10m/min rate isnt exactly going to be the end of the world.

People go OOA at depth, like 80+ft (27+m). And its because they have no idea how much faster they are using gas down there, they're breathing inappropriate mixes (like air) and also have tunnel vision and some narcosis impairing their judgements about who to follow and when to ascend. People go OOA in what you describe as "worst case" NOT on 35'/30m dives. At least this is what my cursory review of accidents and OOA incidents posted here suggests.

Amazingly when they do go OOA, somehow they muddle through and don't typically die. The majority of deaths are from heart attacks and AGE caused by panic, with CO2 possibly being a contributing factor.

However as Jason has pointed out, quite well I might add, 30 minutes of math isn't going to hurt anyone either. After that you can just memorize a couple of numbers, knowing how they were derived. Vandit, you've yet to make a good arguement why withholding information from budding/less knowledgable divers is a good thing. Because "they'll forget it" is pretty weak, and appears condescending too.

 

[vkalia]

I could be wrong but I think one of the misperceptions here that gas planning involves complex decision making underwater. In fact, it seems to me that with gas planning, any complexity (what little there is) is tackled well before you show up at the dive site.

The misconception is not that gas planning is complex, but that everyone is capable of remembering it and pulling it off.

 

[vkalia]

The surface is only a minute or two away provided that you make the right decision to leave depth immediately when a problem occurs. A great deal of the in-water experience and training in RecTriox and Tech 1 is just instructors highlighting to students how divers will make mistakes in judgement about leaving depth (with video evidence of a plethora of mistakes made by students in the class), and to try to fix that and hammer into students that they need to drop what they're doing and leave when it starts hitting the fan.

Not having seen Rec Triox and Tech 1, I cannot comment on that. I agree with you that a lot of times, divers do make mistakes in when to leave depth. It aint just beginners, either.

However, I think this usually arises when there are other factors at play, and people get so caught up in solving them that they forget to watch their air/depth/time. I'd reckon that in a simple case of someone running low on air, going up to the surface is something that comes pretty naturally.

Even if bad decision making does come into play in this case, the correct solution is teaching better decision making. If someone is going to forget to go up at 50 bar, they can equally forget to go up at 70 bar.

I definitely don't think that AOW students with 100 dives or less would be able to consistantly get off the bottom fast enough so that an "800 psi / 50 bar" rule would be sufficient for dives of 100 fsw.

Based on what I have seen (atleast 200+ different people hitting 50 bar at 30m and easily making it up to the surface after doing a slow ascent and a safety stop), I'l have to disagree. I suspect, however, that neither of us is going to convince the other, so let's leave it at that. Each of our opinions are shaped by the divers we see and situations we encounter.

Safe diving to you,
Vandit

 

[Adobo]

The misconception is not that gas planning is complex, but that everyone is capable of remembering it and pulling it off.

It's truly a wonder that your students are able to get out of bed and make it to the bathroom every morning....

Edit: Based on the picture you paint, it's truly a wonder that your students are able to get out of bed and make it to the bathroom every morning....

 

[darkpup]

Based on what I've seen (offhand, atleast 50 cases of people hitting 50 bar at 30m, and making it up to the surface after doing a safety stop with enough air), I'l have to disagree. I am not going to be able to convince you, and you are not going to be able to convince me, so let's leave it at that.

No one's arguing that 750 psi / 50 bar is not enough gas for a single person to surface safely from 30m / 100' with a safety stop.

We're arguing that 750 psi / 50 bar is not enough gas for two people to surface safely from 30m / 100' with a safety stop. It would be like recommending 375 psi / 25 bar for a single person to get to the surface from 100' / 30m with a safety stop, which is something you're against.

Even in your previous example of 750 psi / 50 bar being enough to get two people to the surface from 120' / 130' (39m), you acknowledge that they'd have to blow their ascent and safety stop to survive, let alone have enough gas at depth to resolve the OOA emergency.

How again is this the best way to teach gas planning for an emergency?

~ Jason

 

[NadMat]

Has air been outlawed? Are the scuba police going to come after me for yet another infraction. Will I be excused since nobody told me that suddenly air at 80' is a no-no. Funny that it worked fine for me on hundreds of dives.:06:

People go OOA at depth, like 80+ft (27+m). And its because they have no idea how much faster they are using gas down there, they're breathing inappropriate mixes (like air) and also have tunnel vision and some narcosis impairing their judgements about who to follow and when to ascend. People go OOA in what you describe as "worst case" NOT on 35'/30m dives. At least this is what my cursory review of accidents and OOA incidents posted here suggests.

Amazingly when they do go OOA, somehow they muddle through and don't typically die. The majority of deaths are from heart attacks and AGE caused by panic, with CO2 possibly being a contributing factor.

However as Jason has pointed out, quite well I might add, 30 minutes of math isn't going to hurt anyone either. After that you can just memorize a couple of numbers, knowing how they were derived. Vandit, you've yet to make a good arguement why withholding information from budding/less knowledgable divers is a good thing. Because "they'll forget it" is pretty weak, and appears condescending too.

 

[vkalia]

Vandit, you've yet to make a good arguement why withholding information from budding/less knowledgable divers is a good thing. Because "they'll forget it" is pretty weak, and appears condescending too.

Withholding information? If you read my posts, in virtually every post I have made the point that I think gas planning is taught inadequately and more emphasis needs to be given to it. In my very first post, I mention that I teach gas planning in AOW-Deep, as well. So you dont need to convince me of the merits of teaching some form of gas planning.

However, my experience has been that the vast majority of divers are not going to remember this, and that detailed gas planning is a waste of time for the vast majority of divers. Most of the divers I've seen dont even remember how much weight they wear on their weight belt. A good percentage need to be reminded to check their SPGs. So you'll excuse me if I doubt the universal benefits of teaching gas planning calculations. I wish it weren't so, and I wish every diver would take responsibility for their own dive, their own skills and their own safety, but that doesn't happen in the world that I live and dive in. Call me cynical.

The latter opinion doesnt negate the former. 1 is what I wish for, and 1 is what I think will happen.

An ancillary point is that "dive with a buddy + thumb at 50 bar" isnt as useless as some people would like to believe it is.

Cheers,
Vandit

 

[darkpup]

Has air been outlawed? Are the scuba police going to come after me for yet another infraction. Will I be excused since nobody told me that suddenly air at 80' is a no-no. Funny that it worked fine for me on hundreds of dives.:06:

Fair enough. The "air is for tires" and "30' per minute ascents will kill you" comments are just as condescending as the "math will kill you" comments.

It's easy to confuse personal preference for "the only way to do things" on both sides.

~ Jason