Comments on: Rock Bottom- Rethinking the 500psi Gas Rule

By: James

James — Thu, 14 Jan 2010 13:45:27 +0000

Hi Alex,
To work out the consumption rate, you can simply take your students to 33ft/10m and have them swim a course for 10 minutes and log the amount of gas used. This figure then needs to be associated with a tank factor that corresponds to the size tank used, because 800 psi from an AL80 is not the same amount of gas as 800 psi in twin 104’s. In the end, they will have a number that they can transpose to any tank they will use.
Most divers have a Surface Consumption Rate of about .6 and .8 cubic feet per minute, less on deco and more during emergencies. None the less, these are simple lessons that any new diver can easily understand as a part of proper dive planning.
Feel free to contact me at jm@unifiedteamdiving.com if you still have questions, our you can visit our website at http://www.unifiedteamdiving.com

By: Alex

Alex — Thu, 14 Jan 2010 11:14:53 +0000

A great article. I’m interested to know how you work out the consumption rate for the entry level students?

By: James Mott

James Mott — Fri, 18 Dec 2009 07:25:12 +0000

Hi Andy,
Planning for Rock Bottom will always give you a compelling advantage over not planning. It will give you the understanding and awareness as to what level of risk you are choosing to take. In reality that is what all diving really is. Risk Vs. Benefit. What are you willing to risk vs. what pictures can you add to your slideshow.
Breaking conventional rules that don’t apply to your unconventional situation isn’t really breaking any rules. Planning Rock Bottom for 100’ and then spending the dive in 20’ of water is not breaking any rule and I’d agree… have fun, be safe and do your dive.
The advantage of knowing what you need to get two divers up to the surface from max depth, doing a proper ascent and accounting for all minimum deco/safety stops, will only improve your awareness underwater. If you choose to dive solo, divide that number in half and that’s the minimum amount you need to surface from that depth so that you can wander around on your own, taking pictures and surface on your last gasp.

By: Andy Murch

Andy Murch — Fri, 04 Dec 2009 20:29:54 +0000

So what do you think of the idea of completing your planned profile and then wandering around in the shallows (as a photographer that can be quite productive) and then surfacing on the last gasp?
As a DIR Instructor I expect you to shake your head in disgust at this formula. Where is the gas reserved for my buddy – usually (again being a shooter) I don’t have one because they get bored out of their minds following me around. I see the head shakes getting more animated
The thing is, some of my best friends dive by the DIR numbers. That is definitely their choice but after thousands of not particularly aggressive dives I’m happy to break conventional rules because I don’t think they’re always important.

By: mrsscubasteve

mrsscubasteve — Mon, 23 Nov 2009 08:03:33 +0000

Funnily enough the above has always been my approach to air consumption. – Maybe I just like spending too much time chasing the fishes.

By: Nick

Nick — Wed, 18 Nov 2009 17:46:21 +0000

Nice blogg sound perfectly reasonable to me