Have you ever sucked the bottom out of your air tank?

[scubajoh44]

I did it once just to see what it felt like. I was only at 10 feet and ready for it. I had never run so low on air that i felt the resistance (at least not significant). It was good to know what it felt like. It was horrible.

 

[drm]

Never ran out of gas, but I have been on dives where someone ran out of gas. The first time, a guy tapped me on the shoulder and showed me his pressure gauge, which was on zero. The second time, I had my regulator ripped out of my mouth...not a pleasant experience.

Dave
www.divingindepth.com

 

[limeyx]

One of my instructors shared with me a good rule of thumb about when to start your return to the surface based on the amount of air...

Multiply your "max" depth by 10. Thus number is your "start heading" up number so you as you get shallower, you will have enough for any required safety stops or a below surface swim to the boat.

but why not calculate it correctly, so you know *why* you are heading up on that much gas?

 

[limeyx]

For my benefit (because I am not too crash-hot at mathematics... duh...) could someone please give me the above rule of thumb as applied to metric? I can't work it out - or is that I don't understand the entire rule??

Ta.

Rather than use such a rule of thumb, it might be better to start with a question:

How much gas do I need to get me (and an OOA buddy) safely to the surface from X depth. There are plenty of posts on scubaboard and elsewhere that cover those concepts (and obviously the amount depends on your ascent profile and margin of safety you are prepared to live with)

 

[Phreak]

No, never happened. And I've also never ran out of gas in anything except my lawnmower (no gas gauge there).

Seriously- for just a minute...SHAME on you! Ok, now that I've beaten you up a little....this is why you read the gauge, swim a few fin kicks..look at cool fishy, read the gauge again, check your buddy, repeat. Start that habit today. Check it, check it again. Check it often. Myself I'm looking at that thing a lot, even on shallow dives because everything I need is practically on the console...compass, (heading)PSI, depth, temp, time...theres a lot going on w/ my computer.

BTW- computer is geting serviced right now as it was reading 300-380 PSI higher that it actually was. So for the last two months I was at risk of running out of air if I pushed that time/ depth. Any solace I have is that Ive been coming out of the water with what I read and assumed was almost 1000 PSI anyways.

And theres another post- get your computers and regs serviced annually!

 

[Diveral]

On my second dive, I ran out of air. At the time SPG's were not the norm and we dove with J valves. The idea was the valve was up and it would stop sevring air at about 500 psi left in the tank. You would then pull the lever and release the reserve. However, my lever was already down! I don't know if I snaged it on the wreck or what. This used to happen to people with some degree of regularity. So I would bet that many people on this board have run out of air, and are just not willing to admit it.

I've got two old J-valve tanks. I always dive with the valves down and use my pressure gage to track my air. During one dive the valve must have been accidently bumped up and it got hard to breath around 450 psi. It took me a few seconds to realize what had happened. Boy was that valve hard to reach.

 

[teknitroxdiver]

Some people have suggested multiplying depth by 10, and other 'rules of thumb' to figure out how much air you need to start up with. However be advised that these rules of thumb aren't acutally telling you anything, because you're working in PSI, not CF.

For example: Let's say you're at 100 feet. By that rule of thumb, start up at 1000 psi. If you're diving an AL63, you've got 21 cubic feet of air left at that point. (63/3000*1000). But if you're diving an HP130, you've got almost 38 cf of air.

At a combined SAC rate (you and your buddy, to take into account having to bring him along on your gas) of 2.0, that means that on the 63 you've got 3:30 left at 100 feet before you suck the bottom out of the tank. You've got 6:20 with the 130.

At an ascent rate of 30 fpm, it will take you 2:49 to reach a 15' safety stop. You have now consumed 17 cf. You'll use 9 more cf during your 3 minute stop. Now you've used 26 cf. Ascending to the surface will use 2 more cf. Now you're at 28cf, which means you're in debt by 7 cf. Banks don't loan air, so you're in trouble. You ran out of air halfway through the safety stop.

How about the 130? 2:49 to ascend will still take 17 cf, 9 more in the stop, and 2 more to ascend, so you still used 28cf. But you started with 38, so you've got 10 more cubic feet of air to extend that stop, or power inflate your bc.

So it's best to actually calculate a real number for your rock bottom, not use an arbitrary 'rule of thumb'

 

[TheYellowSubmarine]

Once towards the end of the dive, just below safety stop found a big lobster and spent ages getting him. During the safety stop my computer read "0", and even though I could still breathe, decided to breathe off my buddy's octo for the last minute of the safety stop. I was keeping an eye on my air, it was the first dive of the day, no deco, close to surface, with a buddy who didn't like breathing P) so I wasn't too worried. The lobster was huge, so I thought it was worth it.

 

[Scuba Brad]

Jason, Running out of air at 60' is not a very good idea. Next time make sure your buddy is looking out for you where lobster fever gets to you.

I like mine with butter!

Happy Diving

 

[mello-yellow]

Couple times, but only when I had another tank on me.

Once, with only one tank I got down to 100 psi and took the buddy's octopus rather than ascend. (Okay, we ascended together.)