Amount of air used per dive

[daveh735]

How much air should you use in an average dive?

I have been doing pool lessons recently, no longer than an hour and seem to be using alot of air compared to my girlfriend.

I have asthma, do not have real issues with it anymore but wondered if I was not knowingly using more for some reason?

[AllynCarter]

Hi Dave,

The long answer is that the air you use on a dive is usually measured as "Surface Air Consumption" (SAC). This is, rougly speaking, the amount of air you would have breathed if you had been at atmospheric pressure. You can measure this by recording the volume of your cylinder, the start and end pressures and your depth profile during the dive. This can be automated if you have a dive computer and some software, such as JDiveLog. There's a lot more detail at http://www.dive-logs.com/infosac.jsp;jsessionid=C10F0A37D73080F143771748DEB 7D0D1
Obviously in a pool, you'll not be very deep, so your consumption should be pretty light.

The short answer is to stop worrying about it and concentrate on the rest of your technique. Relax and start to enjoy diving and make sure you are corrctly weighted. That's the best way I've found to improve my consumption.

Hopefully, the asthma thing is a complete red herring. If you've been passed fit to dive, the asthma must be very well controlled and should have no impact at all. If it is affecting your diving, I doubt if you should be diving.

By the way, girls always seem to use less air.

[daveh735]

Thanks for clearing that one up :)

My asthma is well under control, I am fortunate to be able to dive really but am glad that I can.

[bakerstreet]

The short answer is to stop worrying about it and concentrate on the rest of your technique. Relax and start to enjoy diving and make sure you are corrctly weighted. That's the best way I've found to improve my consumption.

Is the correct answer.

I found my air consumption greatly improved once I got over the fact that I wasn't going to die down there! Lol! I also used to worry about the kit far too much. I solved that issue by flogging the Scubapros and bought Apeks instead :D

My air consumption hasn't really changed much in recent years. If I'm in tropical waters, my usual target is 50 bar to 15-20 minutes depending on the depth.

[northern_diver]

If im not deeper/or at 25 meters UK then yeah, depends on the day, the kit up, the entry, the buddy, the weather, the night before.

I normally work on 3-3.5 mins per 10 bar...but actually normally calculate in my head 2.5 mins per 10 bar for the purpose of deco etc. Not fully accurate but if the plan doesnt work out, gives me something to work from.

As its lose math, it also gives me room to over stay accidently etc

Lower consumption comes with experience/proper weighting (minimal effort)/minimising effort on dives. So relax, chill, think more on the other dive aspects and it will fall into place.

Females often require less air, but more air...and contry to the popular belief, thats not because of those 2 normally clearly visible reasons.

John

[MattS]

You wold be wise to avoid making any judgement based on what happens in a swimming pool. The environment is entirely false compared to open water diving. Carrying out the training exercises also consumes far more air than would be normal.

Use the pool as an opportunity to get acquainted with the new environment. Breathe as much as you need to breathe. Focus on relaxing and developing a breathing technique which is deep and smooth. Trust your instructor and try to ignore any natural anxiety. Nature will do the rest.

As a more general piece of advice about diving, try to avoid judging your own performance by comparing it to other people's performance. It's not a competition. I am guessing you are not running out of air in the swimming pool before the session is over, so there is no issue for you to be concerned about.

I have asthma, do not have real issues with it anymore but wondered if I was not knowingly using more for some reason?Air consumption varies greatly across the diving population. I am sure we could find someone who does not have asthma that breathes more than you. We could also find someone who breathes less than your girlfriend.

[ChristianG]

As Allyn mentioned it is usually shown as Surface Air Consumption (SAC) and measured in litres per minute (lpm).

Having regard to what Matt said (eg don't worry about it), here are some figures you could compare to:

• 06-08 lpm - a female acquaintance of mine who is a freak, as well as a fish
• 11-14 lpm - myself, which is OK for a guy 188cm tall, haven't checked for a while though
• 16-20 lpm - probably the average for a reasonably experienced diver, having regard to physical condition
• 21+ lpm - beginners, physically unfit divers (obese springs to mind), really big/heavily built divers (rugby props/second rowers for example)

I have yet to meet the beginner diver whose SAC did not reduce as they got more experienced.

[Tony Dwyer]

Lots of good advice already offered here!

Females usually use less air then males. Size for size they have less muscle mass. Muscles are your bodies engine, the more muscle mass you have the more oxygen you need to run them. :)

Also, guys tend to have bigger lungs, so every breath, even a light one, will move more gas than a females small bellows in an equivalent action.. For example, my chest measures out at 47" (no gags please fellas!) while SWMBO is a comely 36" and a significant portion of that is not involved in breathing. :)

I swear that SWMBO is a fish in disguise, she uses MUCH less air than I do.

Remember conditions will affect your breathing rate. Cold water makes newbies blow like a supercharger!

The secret to comfortable diving is, good training, practice, correct weighting and RELAX. :)

[daveh735]

Thanks for that :)

We did the third and fourth sections of the lectures last night, learning about the dive tables (very confusing but im getting there with it)

[Ian Wetherall]

As every bod has said

Dont worry about it ; the boss has the lung capacity of a small child so uses far less than me.

To compensate Im aquiring 15 litre cylinders to her 12 and we seem to about on par now in terms of usage

[Edward]

• 06-08 lpm - a female acquaintance of mine who is a freak, as well as a fish


Dived with one of these in the mid ninety's would do a 30m for 10 min, then 20m for 20 min and finish with a 10m for 30 min. All on a single 12 at 207 bar.

Mere mortals like myself needed a new cylinder for each dive.

Edward

[voltiana]

Mu Hubby(micromouse) tends to use more air than I do during our pool sessions, and I am not sure why. I do find myself generally relaxed in the pool and wonder if it will be the same when we do hit open water.

Volty

[ChristianG]

Mu Hubby(micromouse) tends to use more air than I do during our pool sessions, and I am not sure why. I do find myself generally relaxed in the pool and wonder if it will be the same when we do hit open water.
Chuckle.

Micromouse probably is just a bit larger than you, with bigger lungs (no tittering (sorry) please, thenk-yew-very-much), bigger muscles and - well - just bigger.

Therefore he needs a bigger volume of gas, simple really.

[northern_diver]

heheheh

10 MIN WARNING
-diver scramble to sort gear
-buddies gear each other up
-DM(in the BSAC and PADI terms) shouts out the dive details

ON STATION WARNING
-first in, check shot is good.
-shot good
-2nd
-3rd
-4th
-5th stick of divers goes in in neat, quick succession of the back.

-UNDERWATER
-decent check at 6mts
-going down steady, protecting ears...or like some head down like a diving missile to the wreck:cool:
-hit wreck and randomly break off shot to play.

Such as buzz, jumping off a perfectly servicable boat, in the middle of the north sea with alsorts of gear strapped, hooked, clipped and tied to you.

No wonder people have a higher SAC at the start than the end:)

[micromouse]

Chuckle.

Micromouse probably is just a bit larger than you, with bigger lungs (no tittering (sorry) please, thenk-yew-very-much), bigger muscles and - well - just bigger.

Therefore he needs a bigger volume of gas, simple really.

See darling....I told you so!!!!!

Wayne

[paul_c]

my SAC was god awful when i dived in a drysuit. in excess of 30l/min now im in a nice wetsuit and diving on twin 10s in down to 15l/min (average). all it took was to just dive and relax more. which in a drysuit i just can not do.



the important thing is this. you dive to your own limit. if you need to calulate a SAC at 30;/min then do it. you find your safe dive times and dive them. then all of a sudden your back with more air than you planned. then you recaululate it and its gone down. you just say we are diving XYZ time to XYZ depth

[daveh735]

Thanks for all the replies. It seems I have started a discussion. This diving is bloody more technical than I ever imagined. I am adapting however :)

[PeteM]

Thanks for all the replies. It seems I have started a discussion. This diving is bloody more technical than I ever imagined. I am adapting however :)

Don't worry it can only get worse from here

[Nigel Hewitt]

Thanks for all the replies. It seems I have started a discussion. This diving is bloody more technical than I ever imagined. I am adapting however :)
ROTFL

Nobody even mentioned rebreathers yet and doing a two hour dive on 60bar each from two 2L cylinders.

Never worry about your air consumption. Just check the SPG and don't be afraid to signal <50><UP><OK?> Nobody minds you breathing hard. We all did it. Better gas consumption just happens. Any trick you try will seem to work so take all advice with the pinch of the proverbial salt and just do time in the water.