How do I improve my air consumption?

[CelticRavenVA]

Ok I looked at the previous threads on SAC, and am trying to figure out if I really do suck though air as fast as I think I do. I know I go through air pretty quick and am working on that part, but according to my Cobra, my SAC is between .51 being the lowest on a dive and .6 for the highest. I don't get it.... if people in the previous thread I was reading are really at .2 and .3 WTF? I work out three to five times a week, I am in pretty good shape.... (Yeah I still smoke but planning on taking another crack at quitting that soon)

See what scuba board does to you? You start looking at old posts and you get all pranoid.

 

[rmediver2002]

Man, unless your coming up early due to gas concerns instead of decompression obligations I would not over think it.

Better to rent or purchase a larger tank if needed than to be concentrating your breathing (and usually ending up skip breathing) during your dives.

I work with a couple guys commercially that have been diving over 25 years and they refer to themselves as air hogs. More tank changes and the quote air is free come up often but of course we tease each other about every little thing anyway!

 

[miketsp]

I am in my mid 50s, I do 30minutes hard exercise 3 x per week and on a relaxing dive my SAC is at 12litres/min or 0.42cu ft/min which from what I have seen is good but not exceptional.
This SAC will go up by about 50% if I have to work against current for most of the dive.

My son (CMAS Instructor) , 23 years old without an ounce of body fat has a SAC at 8 litres/min or 0.28 cu ft/min. That is considered exceptional, so much so that I have seen DMs check his gauge at 40m because they thought it was stuck!

I know one other instructor with SAC in this range.

Oh yeah my wife's SAC was 13 until the last revision of her reg when it increased to 14. The tec told us that he had left it set very light.

 

[CelticRavenVA]

Ok, something to add here is yeah I am still fairly new to diving, and get excited sometimes. (Who doesn't) I am told you get better at this with experience... So just go with it or concentrate on it?

 

[miketsp]

Ok, something to add here is yeah I am still fairly new to diving, and get excited sometimes. (Who doesn't) I am told you get better at this with experience... So just go with it or concentrate on it?

Diving is not a competition, you don't win any prizes if you get your SAC down. But as you become more relaxed, with smoother movements, less stress etc your SAC will drop.
Pick up one of the various lists that are on the web, "Ten tips to lower air consumption". There are many of them around, and keep reviewing the main items.
The important thing is to know what your SAC really is to be able to plan correctly.

 

[PB565]

I just was just calculating and interpreting my air consumtion rate from the NAUI wheel. What I got was 34, which is, according to NAUI, "cetified beginner", which is less than where I am. I question this because I feel I really blow through my air. This was based on my last dive: 57 fsw, 30 min, EAN36, steel 119 tank w/ 3750 psi to start, 100psi end. Any insight, opinion or advice is appreciated. Thanks.

 

[theskull]

Your tank is rated 119 cu ft at what service pressure? Was 57 ft. the max depth or average depth of the dive? Need the average depth to determine your SAC rate.

Will need this info to calculate.

However, do not need any info to tell you how to improve your SAC rate, no matter what the current rate is.
1. Relax.
2. Proper weighting and trim.
3. Control buoyancy with lung volume as much as possible and make BC adjustments only when needed.
4. Relax.
5. Breathe slowly and evenly, as if through a soda straw.
6. Conserve energy and use an efficient and slow kick.
7. Do not swim with your arms.
8. Relax.
9. Dive often, and with divers who are more skilled than you.

theskull

 

[PB565]

Your tank is rated 119 cu ft at what service pressure? Was 57 ft. the max depth or average depth of the dive? Need the average depth to determine your SAC rate.

Will need this info to calculate.

However, do not need any info to tell you how to improve your SAC rate, no matter what the current rate is.
1. Relax.
2. Proper weighting and trim.
3. Control buoyancy with lung volume as much as possible and make BC adjustments only when needed.
4. Relax.
5. Breathe slowly and evenly, as if through a soda straw.
6. Conserve energy and use an efficient and slow kick.
7. Do not swim with your arms.
8. Relax.
9. Dive often, and with divers who are more skilled than you.

theskull

Well, service pressure is 3442 (PST E-8 119), obviously overfilled at 3750. 57 is max, my computer doesn't seem to give me an average (Oceanic Veo 200), the dive was pretty much straight to the bottom and a direct, safe, ascent. I would benefit from all 9 of your tips. Thanks.

 

[theskull]

So, here goes:
3442 / 119 = 28.9 psi per cu. ft.
3750 - 100 = 3650 psi; 3650 / 28.9 = 126.3 cu. ft. used on dive.
126.3 / 30 min. = 4.2 cu. ft. per minute at depth.
57 ft. / 33 ft. = 1.7 ATM + 1 = 2.7 ATA
Therefore, 4.2 / 2.7 = 1.6 cu. ft. per min. SAC (Surface Air Consumption)

If I made no math mistakes (and believe me, someone will correct me if I did) your SAC rate is 1.6 cu. ft. per min., which is in the beginner range. A SAC rate of 1 is pretty average, and the experienced divers achieve .5 or a little less.

More important than knowing your SAC (for now) is knowing how long a tank will last you at depth, leaving plenty of gas for a safe ascent (assuming that you may have a small problem during ascent, may need to share gas with an out-of-air buddy, and may need to make a surface swim on air or maybe a quick descent to help another struggling diver)--in other words, ascend with at least 500 psi left in the tank on the shore. And work (relax) to improve your rate.

Happy diving,
theskull

 

[Quarrior]

You get a gold star for your math skills. Seems you need more Nitorgen.

So, here goes:
3442 / 119 = 28.9 psi per cu. ft.
3750 - 100 = 3650 psi; 3650 / 28.9 = 126.3 cu. ft. used on dive.
126.3 / 30 min. = 4.2 cu. ft. per minute at depth.
57 ft. / 33 ft. = 1.7 ATM + 1 = 2.7 ATA
Therefore, 4.2 / 2.7 = 1.6 cu. ft. per min. SAC (Surface Air Consumption)

If I made no math mistakes (and believe me, someone will correct me if I did) your SAC rate is 1.6 cu. ft. per min., which is in the beginner range. A SAC rate of 1 is pretty average, and the experienced divers achieve .5 or a little less.

More important than knowing your SAC (for now) is knowing how long a tank will last you at depth, leaving plenty of gas for a safe ascent (assuming that you may have a small problem during ascent, may need to share gas with an out-of-air buddy, and may need to make a surface swim on air or maybe a quick descent to help another struggling diver)--in other words, ascend with at least 500 psi left in the tank on the shore. And work (relax) to improve your rate.

Happy diving,
theskull