Air management for beginner.

[fisherdvm]

I don't know if it was covered in my OW or not, it was too many years ago. Before you blast me to review my OW class, which I should, how about sharing your opinions.

Assuming a square profile, straight down, and straight up. Not exceeding the no decompression limit (NDL). How much air you would need from 33 ft, 66 ft, and 100 ft.

I am guessing, at 33 ft, for a beginner, you should have about 600 to 700 psi.

At 66 ft, with a 15 ft 3 min safety stop, 800 to 900 psi.

At 100 ft, with a 15 ft 3 min safety stop, 1000 to 1200 psi.

Maybe I'd add an extra 100 psi for current, rough surface enviroment, hazards, etc.

Remind me where in OW did they discuss this.

 

[PerroneFord]

Gas management for OW Divers:

"Be on the boat with 500psi"

Class concluded.

 

[The Kraken]

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

 

[H2Andy]

fisher, you're basically talking rock bottom (enough gas to get you and a buddy to the surface in case of an OOA)

generally speaking, for an AL80, rock bottom is 700 psi down to 60 feet and 1,000 psi down to 100 feet, and it allows a couple of minutes to get situated at depth, a slow ascent, and a 3 minute safety stop at 15 feet.

but you can calculate your own using your own SAC, the planned depth, and the type of cylinder you are using

at least in PADI OW, they don't discuss this

 

[Ken abucs]

The rule of thirds is the easiest way. You never know what your air consumption rate is going to be, especially as a beginner. If you fighting a current, or cold, air consumption will be a lot higher than a warm drift dive.

1/3 of you gas out
1/3 of your gas back
1/3 of your gas is for reserve/emergencys.

So if you're diving a standard 3000 PSI cylinder, turn your dive at 2000PSI.

 

[Blackwood]

Assuming a square profile, straight down, and straight up. Not exceeding the no decompression limit (NDL). How much air you would need from 33 ft, 66 ft, and 100 ft.

Depends on the divers, but you'll want something in the ballpark of 13CF from 33 (40), 16CF from 66 (70) and 30CF from 100.


(Above assumptions: 2.0CFM "emergency" consumption rate, 3 minutes up from 40 and 70 feet and 5 minutes up from 100).

Remind me where in OW did they discuss this.

They probably did not.

 

[jbd]

I pretty much agree with PerroneFord for the initial diving that a new diver does giving the conditions you set. However as the new diver gains experience I believe they should develope better gas planning and managements skills. I also am a firm believer in these things being taught in the OW class. Back on the boat with 500 psi works initially for most new divers and for the first several dives will suffice to start generating reasonable SAC rates to work with to do more appropriate planning.

 

[Blackwood]

I pretty much agree with PerroneFord for the initial diving that a new diver does giving the conditions you set. However as the new diver gains experience I believe they should develope better gas planning and managements skills. I also am a firm believer in these things being taught in the OW class. Back on the boat with 500 psi works initially for most new divers and for the first several dives will suffice to start generating reasonable SAC rates to work with to do more appropriate planning.

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.

 

[Charlie99]

The 2 minute air management lesson from my OW cert:

1. Never dive in any place that you can't go directly to the surface.

2. Start your ascent no later than 100psi per 10'. For the first few dozen dives, add another 500psi beyond that as you will be breathing fast. (Assuming AL80 or similar sized tanks). Don't fudge on this just because you are a new diver and are running out of air before everyone else. This makes it even more important to ascend early.

3. On and out-and-back dive (shore or anchored boat) turn the dive at 1/2 + a couple hundred psi. Stack the odds in your favor by 1) swimming upcurrent for the 1st part of the dive, and 2) come back shallower than you went out.

4. The above rules are intended to get you and a buddy whose reg has suddenly failed safely to the surface, but you may have a long surface swim back. See rule #1.

 

[fisherdvm]

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.

That is new to me, but it make physiologic sense about the ascent rate. I also heard of the 1/2 rule - ie. a 1 minute safety stop at 1/2 of your maximum depth. I am not sure which agency teaches this - is it NAUI ?