How Much Air?

[lerpy]

More or less just going to repeat what has already been said, as you get more experience you will calm down, use less weight, hold buoyancy better and all those things that will allow you to relax your breathing and get better SAC rates. As Max Bottom Time said get someone to video you diving, this is a great idea as he said to see if you are moving a lot, sculling etc, as well it will give you an idea of your gear config. Sometimes you will see your get sticking out in places, that increases drag and can have an affect. At the end of the day you may be a heavy breather. I dive double 130's for tec and cave, and when I dive an AL80 on a trip in the islands I am there first one heading to the surface normally, much to the upset of my buddy, but that's life don't let it pressure you to run your air low.

 

[The Chairman]

You might want to read this: Reasons to take a propulsion/trim/buoyancy class...

 

[Reku]

You might want to read this: Reasons to take a propulsion/trim/buoyancy class...

NetDoc is basically the master of all things floaty. One of the best threads I've ever read.

 

[decompression]

Further, a point I didn't see mentioned, SPG's are notoriously in accurate, so 250 PSI could be much less.....and considering a first stage won't supply air under 150 PSI or so......plan for rock bottom and all will be well.

 

[2airishuman]

I'm still a relatively new diver with about 40 dives per date. On most trips, even though I feel pretty relaxed, I go through air faster than most of the other folks on the dive. As per directions, I let the dive master know that I'm at 1500 psi. Looking at my log, I'm finishing dives at times with only 250 psi. All of this makes me uneasy. Any suggestions?

You could ask for bigger tanks. Many ops will accommodate that request for a nominal fee.

 

[Steve_C]

It sounds like you are usually on guided dives in which case you maybe are trying to keep up with the guide. In that situation it is easy to be using your arms (or legs ) and without knowing it be using them for trim and buoyancy. Doing a constant small flutter is not very efficient and you might be only getting part of that in the forward direction. I tend to do a full leg kick but leaving a glide between each kick. Kick, glide. As is I have to stop frequently so that constant flutters can catch up. especially if they are moving at an angle. Note that if your buoyancy and trim is correct than when you do kick it is all for forward movement and not part of it used for trim.

If you are carrying extra weight but dial in your buoyancy your SAC can still be good. especially if you go slow and steady while going. But the larger air pocket does mean you have to be better at buoyancy control. To me a good dive is one that allows me not to be going anywhere a good part of the dive if I do not want to.

 

[jonhall]

Agree with possible solutions already mentioned. Here's another for a different reason. My dive buddy use to have a big problem with air consumption when he came back to diving after a big layoff. He would wind up swimming about 10-15 feet above everyone else at some point in the dive to save air. Both of us are basically vacation divers and take a couple of trips a year. The main reason for his going through air faster than everyone else was his physical conditioning. He purchased a treadmill at some point and started using it on a regular basis and still does today. For the last 6-7 years he's not had a problem with his air.

 

[dmaziuk]

Air consumption related to busy brain?

Well that one's kinda true: I was fiddling with the camera just this afternoon aiming for that turtle and my SAC went through the roof. My better half even breathed her tank down and had to cut her SS a bit short. The fact that we were chasing it had nothing to do with anything, no sir.

(Topside I asked the BH why she didn't go for my octo and she said "right, we need to practice that more". It's the last dive of this trip & it was a fairly shallow one so no biggie.)

 

[JohnJL]

I also use more air then the other divers.
Tidal volume is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied. In a healthy, young human adult, tidal volume is approximately 500 mL per inspiration.
My problem is my tidal volume is 650 to 700 mL because of my size and lung capacity. That is better than 30% more air per breath. Being a respiratory therapist I have done many pulmonary function tests on myself.

My solution is using 108 cubic foot cylinders. That gives me 35% more air then 80 cubic foot cylinders.

 

[Steve_C]

Busy brain can do it. When taking a drift dive course we did a drift dive. Next day, identical dive identical conditions except for one detail. Instructor told me I was to lead and do it all including the briefing. Party was 5 strangers on the boat. So I briefed and led. there is a light current again so I am just hanging there drifting along. But 3 of my group were just down from chicago and in a hurry to swim to cuba. The other two were on their honeymooon and did the whole dive in an upright position holding hands and staring into each others eyes (no kidding). Swimmers were out ahead. Love birds hanging behind. So while I was very relaxed physically I was looking back and forward and and was not relaxed mentailly. Part way through the dive I checked my air and I was sucking air much faster even thought even at the identical depth of 60 ft. I indicated this to instructor and I eased up the slope contour a bit to about 40-45 ft to stretch out the gas supply. Mental state alone can have a big effect.