Air Consumption Curiosity

[Pyramid65]

I've read a bunch of posts on the subject, I don't believe I am burning through air too quick but only having just done the 4 check dives for my OW cert. and 1 additional for the hell of it I'm sure my breathing rate will improve over time.I'm curious where my breath rate falls at this point.When I got back to the shop the guy asked if I had run out of air on any dives and I did not, he asked as if he expected me to say yes.My weights were suggested by a DM knowing my equipment and were spot on during the weight check, I did have to jockey some from front to back to fix my trim but the weight itself was perfect.The first four dives consisted of tasks learned in class for approximately 10 minutes and 10 minutes of swimming.The last dive was all about diving, we were at Dutch and went to a couple of their "wrecks".I have a pretty good handle on buoyancy, at the platform, I hovered just above it swam over it and down under the single boards and back up using breaths, I was also able to follow the contour of the bottom using only breath control and not touching the bottom once.Here are the 5 dives:

Day 1
1) 23 minutes, 64 degree's, ave depth 23', 1103 psi used
2) 29 minutes, 64 degree's, ave depth 29', 1538 psi used
Day 2
1) 28 minutes, 63 degree's, ave depth 25', 1596 psi used
2) 22 minutes, 63 degree's, ave depth 25', 1190 psi used
3) 22 minutes, 63 degree's, ave depth 28', 1335 psi used

Looks as though I'm pretty consistent, just curious what experienced divers get

 

[RJP]

Tank size?

 

[The Kraken]

OK, here are your stats with some assupmtions:
1: You're diving and Al 80 (Usually about 74 cf of gas at 3000 psi)
2: The tank's beginning pressure is 3000 psi

Avg time of dive = 25 min.
Avg depth of dive = 26'
Avg consumption = 1352 psi

1352/3000 = .45 (% of total volume)
.45 x 74 = 33.3 (no. of cf of gas consumed)
(26 / 33) + 1 = equivalent ATA

Now, take the volume of gas consumed, divide it by the ATA equivalent and then divide that by the average number of minutes of your dives.

Your Surface Air Consumption rate is approximately .74 to .75 cfm.

 

[MXGratefulDiver]

I've read a bunch of posts on the subject, I don't believe I am burning through air too quick but only having just done the 4 check dives for my OW cert. and 1 additional for the hell of it I'm sure my breathing rate will improve over time.I'm curious where my breath rate falls at this point.When I got back to the shop the guy asked if I had run out of air on any dives and I did not, he asked as if he expected me to say yes.My weights were suggested by a DM knowing my equipment and were spot on during the weight check, I did have to jockey some from front to back to fix my trim but the weight itself was perfect.The first four dives consisted of tasks learned in class for approximately 10 minutes and 10 minutes of swimming.The last dive was all about diving, we were at Dutch and went to a couple of their "wrecks".I have a pretty good handle on buoyancy, at the platform, I hovered just above it swam over it and down under the single boards and back up using breaths, I was also able to follow the contour of the bottom using only breath control and not touching the bottom once.Here are the 5 dives:

Day 1
1) 23 minutes, 64 degree's, ave depth 23', 1103 psi used
2) 29 minutes, 64 degree's, ave depth 29', 1538 psi used
Day 2
1) 28 minutes, 63 degree's, ave depth 25', 1596 psi used
2) 22 minutes, 63 degree's, ave depth 25', 1190 psi used
3) 22 minutes, 63 degree's, ave depth 28', 1335 psi used

Looks as though I'm pretty consistent, just curious what experienced divers get

Much better if you figure it out for yourself. All the tools you need are in this article ... NWGratefulDiver.com

... Bob (Grateful Diver)

 

[Pyramid65]

I know my SAC rates, they are in my log, wasn't try'in to figure them...was curious what an experienced diver gets

 

[Scott]

I get anywhere from .28 to .78. Quite the swing eh?
My numbers have very little if any value to you unless we are diving together.
Use air consumption rates for what they are intended, planning a dive within your team.

 

[dmoore19]

Looking back at my logbook, it appears that your numbers are similar to what I had to begin with.

After doing AOW and the peak buoyancy adventure dive (at 45 dives) my SAC seems to have been dropping little by little to around .4-.5. I dropped 2-4 pounds of lead and got trimmed out better. It also depends on how much current there is and if I am trying to swim into it or if there is no current or if it is a drift dive watching the world go by. It's all about getting comfortable and learning a few tips and experience.



I don't profess to be good at this yet but I am learning so others might be able to add more.

 

[Zen1300]

Air consumption is always my concern when it comes down to buddying up with the "insta-buddies." I've not dived enough to establish a true baseline or even improve my consumption rates yet.

I do, however, pay attention to the stats and make sure I document in my log book the details of the dive, so when looking back on the numbers, I can make sense out of them - was I feeling nervous, was my swimming difficult, etc.

My worst dive air consumption was a Search & Rescue Adventure dive. Hit the bottom, stirred up the silt and got lost. I had no one around (DM was above somewhere) and my breathing definitely went out of control as I searched for the golf balls with no viz. I was not comfortable with the situation, but was not panicked or felt in danger (it was a shallow area). More just frustrated. I did 88.6 PSI/min (2.30 CF/min) on that dive.

Navigation, was a simple dive, but I worked a lot - more finning to swim over the distance and not just hovering. - 58 PSI/min (1.51 CF/min).

The wreck dive was peaceful and more relaxing. It was my last dive of the day and my comfort level had really "sunk in." That dive was 32.7 PSI/min (.85 CF/min).

 

[kr2y5]

My consumption eventually plateaued at 0.6 cuft/min. in benign conditions, but it easily grows by 50-100% due to obvious factors like current, but also due to anxiety over unfamiliar site, changes in equipment, task-loading, etc. On a recent boat trip, unless I logged air incorrectly, I was breathing about 1.15 cuft/min. on dive #1, and went down to 0.6 cuft/min. on dive #2 as I realized that the site is benign and within my skill level, all my equipment is still OK, everything is going exactly as planned, and my anxiety has subsided. Stress level is a huge factor...

 

[Doc Harry]

I've been diving for 10 years, 500+ dives. My SAC is generally about 0.7 cubic feet per minute on an active dive. I can do a little better if I leave the camera on the boat. My SAC hasn't really changed much over the years.

My wife's SAC is about 0.3 cubic feet per minute.