How do you stop being an air-monster?

[jknights]

I guess the summary of all the comments is ... who cares how much air you use as long as you come up with some left and you have enjoyed the dive.

I have done 16 years OC diving and my air consumption has varied over that period frrom 25-28 litres/min (training with a novice in cold water) to 9 litres (calm diving in warm sea). My average in recent years is 17 litres/min.
Most scuba books say that average rate is 25 litres/min.

I am just moving from OC to SCR with the view to eventually moving CCR.
This is totally different gas consumption being <2.5 litres/min and average of 1 litre/min.
OC is sooooo wasteful.

BTW. People use more air than others due to higher/lower metabolic rates as well as stress and lack or experience, etc. There is a general tendency for women to use less air than men due to their lower metabolic rate... Huge generalisation,

[DJL]

Originally Posted by jknights

Most scuba books say that average rate is 25 litres/min.

Holly Smoke Batman - that's one hell of an 'average' SAC!!

[jknights]

That is the actual volume of air breathed in and out one minute ( I presume BSAC have adjusted this either for depth or must have scared novices providing the input).

Doing teh maths.....
If you take the average lung total volume to be 5.8 litres then this represents one (full lungs) breath every 12-15 secs.
Practically since we tend to breathe in/out less fully, unless exercising strenuously, this makes the mean breath volume to be about 0.5 litres/breath. Personally I breathe in/out every 6 secs. This represents 5 litres/min. Maybe I am fit ;-) (I wish).

I think that the 25litres/min is as you say (holy smoke, Batman !! ) is an adjusted figure but I have not found to what notional depth. I would presume 30m, which then yields a X4 adjustment factor ==> 20l/min for me. (Maybe I am fit) .

If you are doing less then theory has it that you are either skip breathing or very releaxed (you should be horizontal anyway when diving ;-) ) or have a low metabolic rate.


Try doing the measurements for yourself on the surface.

BTW These are standard physiological values.
References see here:
http://hypertextbook.com/facts/2001/...alabrese.shtml
http://www.spirxpert.com/welcome.htm

[Tonto]

I'm breathing at best about 22 SAC and at worst 30 depending on depth, excitement and work, so I'd say 25 was a fair average for me.
I am fairly unfit at the mo' and have got fairly big lungs but arn't too worried as if I havn't seen enough in that time I'll just have to have another dive
If anyone is interested I've been playing with a spreadsheet to adjust sac, depth etc to see the resultant bottom time, all the variables are on the same row :- c2=sac;d2=depth;e2=empty(what you want left on the surface);f2=fill;g2=volume of cylinder;and h2=descent/ascent rate.
=(((F2-E2)*G2)-(((D2/10+1)/2*(ROUNDUP(D2/H2))*C2)*2)+(1.6*3*C2))/((D2/10+1)*C2)
I know its not in Nigels league (nice snowman by the way) but its made me think and might help others

[Mal Bridgeman]

Originally Posted by NotDeadYet

One thing that newish divers forget is to simply slow down. Don't do anything fast, moving, turning, reaching for something... anything. Slow everything right down.

snip

Cheers,

Stuart

Agree completely. I recall reading that it takes four times as much energy underwater to move twice as fast so .... moving half as quickly uses a quarter of the energy.

Checking contents gauges, finning, looking around are all things that can be slowed down for example.

Regards
Mal

[AirAssisted]

Assuming you are not massivly over weighted ... the key is to RELAX

[Janos]

Originally Posted by jknights

That is the actual volume of air breathed in and out one minute ( I presume BSAC have adjusted this either for depth or must have scared novices providing the input).

Just to clear up the BSAC line (what with all these fellas with SD exams coming up).

When you start training, BSAC suggest that you plan a dive with a Surface Air Consumption (SAC) of 25 l / min. This is high, but then trainees tend to have higher air consumption. Obviously as you get more experienced and your SAC drops you can plan a dive using a lower figure (but don't forget to take into account your buddies SAC).

FWIW my SAC started off at around 28l/min and it is now is around 22l/min. However I plan a dive assuming 24l/min as I dive twin 12s (so 24l) and it makes the numbers easy.

I'm just a very heavy breather.

[the handyman]

chill thats all there is to it :o)

[hopper]

Originally Posted by the handyman

chill thats all there is to it :o)

No way man, once you start to chill you start to shiver, once you start to shiver you use more air!!!!!

[chas49]

Originally Posted by Tonto

Um I may be missing something but I make the SAC at about 17 for that depth time leaving 30 bar in the cylinder (assuming 232), I'd be really pleased.

Yep - SAC 16.99 for an average depth of 20 metres for 45 minutes assuming 232bar in and 50 bar out.

Perhaps a more reasonable calc for his profile might be average depth 17 metres, 220 bar in and 50 bar out - giving a SAC of just over 18.

I would still be pleased with that...