Once a gas hog...

[beach89]

...what?

Please tell me how I'm going to re-inhale the exhaust bubbles that are now floating towards the surface...

When you exhale, you don't create a vacuum. The air that occupies your mouth, throat, and lungs after you exhale is CO2 rich air. The first bit of air that you inhale, is that same air that was leftover from when you exhaled. That's called dead air space. Now when you're under water, you also have the air that's in you regulator 2nd stage. Unless you purge your regulator after each time you exhale, then that air, that did not get out of your regulator 2nd stage, is CO2 rich air. That's more dead air space. This is why divers are recommended to breathe deeper and exhale more fully underwater. If you breather shallow, then you end up with a larger concentration of CO2 in your lungs, which makes you tired and gives you headaches.

 

[Gombessa]

I imagine the dead air space in a snorkel would be nearly equivalent to what you have internally, too.

 

[TSandM]

The unexhausted air in a second stage is minimal, and doesn't add significantly to dead space.

The main reason for the instruction to breathe deeply and slowly underwater is that that is the most efficient ventilation, and therefore maximizes the benefit you get from the volume in your tank. The reason is that deep inhalation maximizes the ratio of alveolar ventilation to dead space volume.

Snorkels DO add significant dead space, which I think is part of the reason some people get panicky when using them.

 

[lamont]

buy some hp130s and forget about it and it'll all get better eventually...

 

[Bob Vincent]

You right about with becoming at ease ... you'll lower your breathing rate and gas usage. But it has been touched on here in bits. If you want to make the most out of a tank believe it are not, buoyancy control. Just think every time you bump the inflater thats a few breathes of air.

I like long slow inhales and long slow exhales. I want to take in O2 rich gas but then I want to expel the nasty ... long slow exchanges. It's the built up of nitrogen that makes us want to inhale without slow deep breathes and slow deep exhales we aren't changing as much O2 as we could. If people look at me as I'm cruising around they'd swear I was skip breathing but I'm not. I've done it so much its just happens naturally.

I'd first work on buoyancy first. When you nail it and weight yourself right you'll be amazed at the range you can ascend or descend without ever touching your inflater. Just by controlling your breathing.

 

[Skinsfan1311]

By far, the biggest thing is to R E L A X . . .

Yeah...what he said.

 

[ClayJar]

Incidentally, when I switched to a backplate and wing, my trim was thrown completely off for a dive and a half or so. It's *glaringly* obvious in my SAC numbers from the five dives that day precisely how bad being out of trim is.

On basically identical dive profiles (I was in a spring), from the first dive (where I was completely out of trim) to the third dive (where I was back to normal), my air consumption dropped literally 20%. When I say that trim is step one (and buoyancy, step two), I mean it.

Another anecdote: My usual buddy had terrible trim and was ending dives worn out. Then we fixed her buoyancy and trim at a quarry. The difference in effort-of-diving was (by her accounts) *quite* noticeable, and her already low air consumption chopped off a nice chunk.

I may sound as if I'm proselytizing for trim first with buoyancy close behind, but it's not because vertical people look like newbies or anything. It's simple physics, and even my *very* non-diving mom was able to grasp the concept, but it seems to be one of the most difficult things to get existing divers to accept.

Try it yourself. Use some trim weights (or tank band weights, if you don't have trim pockets in the right place) to get yourself to the point you can hover horizontally, and let us know whether your air consumption drops. On anything but a non-kicking drift dive, I believe you'll see a notable decrease, and then again, if you do not, I'd like to figure out why. (I'm a man of science, so being shown to be wrong would not hurt me in the least.)

Anyway.

 

[budgy]

I find most new divers are over ballasted and they can't get the extra ballast off, until they learn to relax. The extra ballast results in more air used for buoyancy control and a greater effort moving through the water.
Long slow breaths reduce pulse rate. As a rough rule of thumb I'm told, if you double the speed you move through the water you quadruple your air consumption. A conscious effort trying to breath slowly, should naturally slow you down.
On the best inhale exhale ratio, I was taught 1:2, and whilst holding breath on ascent is something we all know is dangerous, a short pause between inhale and exhale improves CO2 exchange in the lungs. I think a longer exhale results in greater lung evacuation. A regulators exhale resistance is also greater than the inhale so a slower exhale is easier. The next step is ensuring a horizontal trim and a short effecient fin stroke that stays within the dimensions of the torso. After that work on your personal fitness level.

After saying all that, whilst nearly all of us start out as hoovers most new divers do not have to make a conscious effort to improve their air consumption, they just have to dive regularly.

 

[slingshot]

Slow deep breaths: good for reducing the relative effect of dead spaces, but I find such breathing is also relaxing and so it has a dual benefit. I second the post on getting a suit that fits and doesn't constrict your chest, this helps considerably with relaxing and enjoying the dive, which in turn helps my air consumption.

 

[jeckyll]

buy some hp130s and forget about it and it'll all get better eventually...

Wait! _You_ want to solve a skill issue with equipment???

:mooner: