Gas management/planning

[Sideband]

I was in a Nitrox class the other day and we hit on the topic of planning how much gas is needed for a dive. I was a bit troubled at how basic the description was.

SAC X depth in atm X # of minutes

What bothered me was this was all that really was given. Nothing at all about the extra gas needed to keep from surfacing with an empty tank. IMO, more importantly, they left out anything about having enough gas to assist your buddy if there is a problem near the end of the dive. What if something happens and you accidentaly slip into a deco obligation? Admittedly, I am not going to be deep diving for a while and and ESA would be possible, but that isn't the preferred OOA response and I won't be shallow forever.

Am I missing something or are my concerns valid?

Joe

 

[MikeFerrara]

IMO, your concerns are valid.

It's not surprising though since if all your instructors training was recreational he/she likely wasn't ever taught or required to learn gas management. How could he be expected to teach it?

 

[Michael Schlink]

There are several methods for gas mgmt./planning. But to keep it simple you should ALWAYS have enough "gas" to bring you and your buddy to the surface, comfortably. Gas planning involves making sure that you are actually carrying the amount of gas needed to make the dive you are planning. In most cases divers are just strapping on the "ole AL 80" and sucking it to the bottom. If you can't choose how much gas you need and carry the appropiate tank(s) then the tank you have must determine the depth and time you can spend UW

 

[roakey]

Search the board for the phrase "Rock Bottom" for some real gas management threads.

Roak

 

[sharkmasterbc]

Strange...I'm just a lowly OWS Instructor but I teach gas management in OW class, maybe I'm just lucky as the shop I work for has a power point presesntation all about gas management and buddy skills. We are able to do this because the videos are sent home and most of the course is self study, the students come to class, go over the chapter reviews and then we teach and discuss the finer points of actually diving. As an instructor one should take the time to educate ones self after your itc, idc, ie training.

 

[neil]

Search the board for the phrase "Rock Bottom" for some real gas management threads.
Roak

Roakey is too modest. I can't find it on the board, but he posted the best explanation of some basic gas management for recreational divers. I edited it slightly for length and now use it as a handout in classes. PM me with your email and I'll send it to you.

Neil

 

[roakey]

Roakey is too modest. I can't find it on the board, but he posted the best explanation of some basic gas management for recreational divers.

Thank you, but I think Pug and Mike have done better jobs. But I *think* I may have found the post you were referring to:

http://www.scubaboard.com/showpost.php?p=401869&postcount=65

Is that the one?

Roak

 

[Sideband]

I don't know that that post was any better than what my instructor was giving me. If I follow those instructions I had darn well better be DIRECTLY under the boat if I am "Turning" the dive at 500psi. As I understand it. 'turning' the dive means turning around and heading back to the start/end point. I am admittedly new, but I don't think that means anything in this conversation.

If I have a 3000psi 80cf tank and I want to end the dive with air left in it then I need to turn the dive at approx 1100-1200 psi remaining. (3000 - 600)/2 If I go deeper than about 3 atma then I should probably turn a bit sooner to account for more ascent and safety stop time and to make sure I have enough gas in the tank for my buddy if he needs it in the last 10 minutes of the dive.

This is a bit different than gas planning, but since I am limited to an 80 cf tank I have to plan the dive around the air supply, not the air supply around the dive.

Joe

 

[miketsp]

There were also some discussions on gas management on these threads:
http://www.scubaboard.com/showthread.php?t=56464
http://www.scubaboard.com/showthread.php?t=57775&page=1&pp=10
with a few Excel sheets and CGI pages.

 

[Norm]

You have a lot of good replies here from some very experienced folks, (many of whom I respect). One additional item you may consider that I do, as you get more experience/training and make deeper dives: I treat my deep dives just like cave or ice dives - I dive 1/3's. That way you should always have enough gas to bring up yourself and your buddy, (excluding deco which is another game altogether). JMO
Norm