Air management for beginner.

[jbd]

I don't suspect that PerroneFord was advocating the "rule," but rather addressing that which many dive agencies consider to be basic gas management training.

True enough, but even so its a fairly vaild starting point for most brand new divers as they typically don't have any real working numbers to work with so I don't find his comment at all unreasonable regarding the initial statement by the OP.

After 10 or 12 dives the brand new diver will have some reasonable number to work with if he has been taught about SAC rates etc and can them make more appropriate gas management plans.

 

[Blackwood]

True enough, but even so its a fairly vaild starting point for most brand new divers as they typically don't have any real working numbers to work with so I don't find his comment at all unreasonable regarding the initial statement by the OP.

After 10 or 12 dives the brand new diver will have some reasonable number to work with if he has been taught about SAC rates etc and can them make more appropriate gas management plans.

I'll agree that it's valid so long as they are staying within about 40 feet of the surface.

 

[PerroneFord]

When I am on my recreational, anti-stress dives, I generally like to be at half max depth with half my gas. So for an Al80, on a 60ft dive, I'll be at 30ft with 1500psi. Getting out of the water from there is trivial.

 

[jbd]

I'll agree that it's valid so long as they are staying within about 40 feet of the surface.

Which is where most brand divers should be during the first dozen or so dives.

 

[dumpsterDiver]

.... Back on the boat with 500 psi works initially for most new divers.

"Back on the boat with 500 psi is idiotic". It makes as much sense as simply "don't run out of air". How is the new diver supposed to know when he is to leave the bottom, if all he knows is what he is supposed to have when his ascent is completed? If he knew how much air it takes to ascend then he wouldn't need a specific rule.

Does this 500 psi rule mean that you rush to the surface to make sure that you don't violate the rule. My feeling is that any dive operator or instructor that tells you how much air to have on the boat is irresponsible (personally I don't need any air in my tank on the boat) it's the dive I'm worried about.

This rule reminds me of the situation where a teenage girl calls he dad at 10:45 p.m. and says, "I'm still at the party and I'm leaving now, I might not make the 11:00 curfew" and her Dad says: "I don't care where you are (or how fast you drive), but you better be in the driveway at 11:00 p.m."

A simple rule like: "we are diving in 80 feet today, you will leave the bottom when our elapsed time is XX minutes or when either you or your buddy reaches 800 lbs, whichever comes first" is a far more reasonable way to manage air for the new diver.

 

[Blackwood]

Which is where most brand divers should be during the first dozen or so dives.

*Should be*



Yah. I just like to qualify statements rather than leave them blanketed.

 

[Blackwood]

Does this 500 psi rule mean that you rush to the surface to make sure that you don't violate the rule.

They're probably diving Buhlmann algorithms, so a fast (gradient push) ascent is the name of the game anyway

 

[ArcticDiver]

Try this:
Descent rate of 60'/min. Ascent rate of 60'/min until 33' and then at 30'/min.
Gas consumption rate of .60 cubic feet per minute.
(Hint, you have to find your average depth)

It if was PADI open water, no, it wasn't in the syllabus.

the K

Not to argue to strenously, but I was taught 30fpm to 30' and 15fpm from there to surface. I modify that to go even slower from 15' to the surface.

So, on a 100' dive by the time you include a "safety stop" the diver needs to plan on at least 11 minutes of air himself. Add to that enough for a buddy.

Of course the diver doesn't really have any good numbers at that point in the dive career. So, the rule of thirds is probably a good one to start with. Adjust as necessary as the diver gets experience.

 

[jbd]

"Back on the boat with 500 psi is idiotic". It makes as much sense as simply "don't run out of air". How is the new diver supposed to know when he is to leave the bottom, if all he knows is what he is supposed to have when his ascent is completed? If he knew how much air it takes to ascend then he wouldn't need a specific rule.

Does this 500 psi rule mean that you rush to the surface to make sure that you don't violate the rule. My feeling is that any dive operator or instructor that tells you how much air to have on the boat is irresponsible (personally I don't need any air in my tank on the boat) it's the dive I'm worried about.

This rule reminds me of the situation where a teenage girl calls he dad at 10:45 p.m. and says, "I'm still at the party and I'm leaving now, I might not make the 11:00 curfew" and her Dad says: "I don't care where you are (or how fast you drive), but you better be in the driveway at 11:00 p.m."

A simple rule like: "we are diving in 80 feet today, you will leave the bottom when our elapsed time is XX minutes or when either you or your buddy reaches 800 lbs, whichever comes first" is a far more reasonable way to manage air for the new diver.

I would make the assumption that most scuba instructors would have imparted enough information to their students so they can make a fairly reasonable guesstimate as to what pressure they should depart the bottom in order to make it to the surface and have something close to 500 psi in the tank upon reaching the surface. If an instructor can't get that little information across to his/her students then he or she shouldn't be teaching scuba diving.

There is no need to rush to the surface at all in the scenario given by the OP regardless of air pressure readings.

Please note that I don't teach the 500psi on the boat rule. I only accept it as a reasonable guideline for diver operators when dealing with brand new divers who don't have enough quality information to make a solid gas management plan based on personal SAC rates.

 

[jbd]

*Should be*



Yah. I just like to qualify statements rather than leave them blanketed.

I understand your point clearly They should be in shallow water, but I know people, personally, who have been at depths greater than 100 ft on their second or third post OW cert dive and ran out of air because they never gave their SPG a glance after entering the water.

I would much rather have a 500 psi on the boat rule than have such situations occur.