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Factors influencing air consumption.

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Apr 26, 2005
I've reviewing what I know about air consumption, please run through my list and tell me what I got wrong and what I missed out.

[Note: hereafter "air" refers to any gas mix (e.g. ordinary air, Nitrox, Trimix etc) that is in your cylinder and you are breathig on your dive.]

The factors that affect a person's air consumption fit into a number of categories, which in turn also have a number of sub-categories in them.

  1. The depth that you are at. Due to inverse gas law you take in a denser gas at depth and therefore you breathe in and release more gas each breath.
  2. The state that your body is in.
    This includes:
    • How fit you are. If you are more physically fit your body needs less oxygen to perform a given amount of work. This means that an unfit diver uses more of his or her air to do the same task that a fit one does. e.g. An unfit diver gets out of breath quicker than a fit one and use up their air faster.
    • How active you are. If you are finnning about, waving your arms and using up lots of energy you will also be using up a lot of air.
    • Your lung capacity. People with bigger lungs take in more air per breath and, since not all of the oxygen is used up in each breath, they waste more air when they exhale than a diver with smaller lungs.
    • How efficient your respiratory and circulatory systems are. If they are very efficient you will use your oxygen more efficiently and therefore require less air.
    • How relaxed you are. In times of stress it is natural for your respiration rate to increase. If you are relaxed you inhale and exhale less often therebye using less air.
  3. The type of "air" that you are breathing. e.g. A diver uses less gas diving nitrox than they would in an identical situation using ordinary 21%-79% air.

So, what are things we can do to bring down air consumption? Be relaxed, be experienced (since gives us confidence and relaxes us), be physically fit, breathe deeply and slowly, limit your physical activity as much as possible, try to keep your respiratory and circulatory systems healthy (put down those ciggies and booze you naughty diver! :friday ) and enjoy yourself. If you are having fun you can't be under stress and your body will be functioning well and efficiently.

Ta-da! :girlie

So ... what have I forgotten/left out. I'm doing this because I'm a bit of an air hog and am trying to bring down my air consumption. Any help/pointers are appreciated.

Thanks all.
You missed some critical things:
- Body temperature; a diver who is very hot will burn way more oxygen than a diver who is cool but not shivering
- Respiratory quotient; a diver whose diet is mainly fats (low carb) will be burning fat for fuel. This produces far less CO2, allowing the diver to breathe less frequently; normally 'skip' breathing is strongly discouraged, but my point is that the effect of skip breathing depends on whether you are burning fat or carbs for fuel. Burning fat, you can slightly less frequently without ill effect.
- Vasoconstriction; a diver whose arms and legs are vasoconstricted will burn much less O2. Vasoconstriction can be induced by negative pressure (exhale) breath-hold dives (dangerous; make sure you know what you're doing and have someone watching). Other ways to induce vasoconstriction are being cool (but not shivering) and/or taking a skinny dip (bare skin) in cool water, briefly, before putting your wet/dry suit on
- Circadian rythm/temperature setpoint; related to body temperature. In the morning your body has a higher temperature setpoint, meaning that in the morning you'll shiver around 36C, whereas in the evening you'll shiver at 35.5C, which means that being 'cool' in the evening will burn less O2; further, you can reduce your temperature setpoint permanently by prolonged cardio exercise and/or inducing mild hypothyroidism (via eating lots of raw cruciferous vegetables)
- Blood pressure; a person with higher blood pressure will burn more O2. Blood pressure can be modified by prolonged cardio (being in good shape), but it can be furthed manipulated by eating BP decreasing foods such as garlic and onions or pineapple
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I believe that the single, most important factor in gas consumption remains your cardiovascular condition. On any dive boat, you can just look at the different divers and tell who will be back on the surface quickly. My advice to any diver: If you want to improve your down time, begin a program of physical fitness that emphasizes aerobic/cardiovascular exercise. Run, swim, EFX, stair-climb, etc. Many people will be amazed at their improvement in the water after only 30 days of regular CV exercise.
Happy Diving
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personally i dont agree about fit and consumption . i have seen it many times , the same thing thinner guys consumpting a 18 ltr bottle at 12 m in 10 minutes ( dont ask me where they put it) and other guys like me coming up from 55 meters for 10 min. doing deco and still having air 50 bar when at surface , so what i beleive everything is how often you dive and not doing the same thing every time , so when smthng is not on your schedule and come up to know your moves , any way the point is , i beleive all is matter of how often you dive
actually both of you are correct. consumption does have to do with fitness and conditioning, and it is also a matter of experience.
first of all, it is a FACT that conditioning plays many roles in several areas of diving, especially air consumption and avoidance of DCS. however, one thing that was left out in the earlier posts is that air consumption is something you practice, it's called breath control. the more you conscientiously practice it, the better it becomes. i know this to not only be true in theory, but in actual practice, because it was a major issue for me, previously. but after spending a great deal of time with a hardcore german diver, a while back, it was either control your breath of get left behind on some of the deepest, wildest dives i have ever participated in. i didn't want to get left behind, so i conscientiously worked on slowing down my breathing, and controling it. after less than a week, i started to notice how much more air i would have at the end of some very deep dives (50 meters).
so you should definitely work on your cardio fitness, and you should practice breath control. i hope this helps.
efattah said:
- Blood pressure; a person with higher blood pressure will burn more O2. Blood pressure can be modified by prolonged cardio (being in good shape), but it can be furthed manipulated by eating BP decreasing foods such as garlic and onions or pineapple
Then I'm glad I have low blood pressure! I've always had it and it isn't a problem for anything.

Looks pretty comprehensive list there.

The only thing I could not see that may be related is diet. In particular stimulants like tea/coffee that would be related to stress levels. Maybe iron levels etc.

On a slightly related subject...A few years ago I got involved with the NHC testing a particular companies tables for a particular depth and there were quite a few well known diveing medicine folk from around the globe conducting tests.

After the 1st dive(if I remember right)I was fairly ....."bubbly" and the subsequent ones hardly any for like dive profiles. I asked why and was immediatly asked if I had had tea or coffee(I had) and that they were likely culprits among many, but your question is about gas consumption not absorbtion and for all the people I see .....I`ve seen fat/slim old blokes who smoke "sipping" air and young/old fitness fanatics who can`t get enough so I reckon a lot is to do with the persons nature/attitude/experience and everyone is different and has their own "breathing style " in the water.

I have never tried ,wanted or had to change my breathing style. I imagine it could be quite difficult.....good luck
I hyperventilate when I have to breathe through my mouth. Not good for scuba. :duh
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