Average Gas Consumption

What is your average RMV?

  • less than 0.3 cu ft/min, 8.5 l/min

    Votes: 12 1.4%

  • 0.3-0.39 cu ft/min, 8.5-11.2 l/min

    Votes: 99 11.7%

  • 0.4-0.49 cu ft/min, 11.3-14.1 l/min

    Votes: 225 26.6%

  • 0.5-0.59 cu ft/min, 14.2-16.9 l/min

    Votes: 254 30.0%

  • 0.6-0.69 cu ft/min, 17.0-19.7 l/min

    Votes: 125 14.8%

  • 0.7-0.79 cu ft/min, 19.8-22.5 l/min

    Votes: 88 10.4%

  • 0.8-0.89 cu ft/min, 22.6-25.4 l/min

    Votes: 18 2.1%

  • 0.9-0.99 cu ft/min, 25.5-28.2 l/min

    Votes: 11 1.3%

  • greater than or equal to 1.0 cu ft/min, 28.3 l/min

    Votes: 15 1.8%
  • Total voters
    847

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I just run planning at 1.0 and have extra (sometimes lots!) when it goes well...
 
dirkhh:
Actually, since all of these values are silly. What's the wet volume of the cylinder?
But for this specific example, the error is indeed rather small - assuming an 11.1l tank your SAC (in Subsurface terms) would be .38 cuft/min (we only provide reasonable accuracy to 2 digits - your pressure readings aren't at 3 digit precision...
Click to expand...

You're right. The wet volume of the cylinder is 678 cubic inches/11.1 liters, from @GJC link. I only reported in 3 digits to not overstate the difference in the two calculations. I would report 0.383 as 0.38 and 0.395 as 0.40.

I would imagine most divers have no idea about this topic, perhaps it is a good thing that a few more might know about it now. The error when using the ubiquitous AL80 filled to 3000 psi/207 bar is not very great. The error is much larger with high pressure cylinders, especially the 300 bar ones, as pointed out in the nice post by @ATJ. A 20% error is a whopper.
 
The 2016 poll is now just a month short of 5 years old with 412 responses

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As I have gotten more experience my air consumption has continued to drop and I now have quite a few dives that are in the .38 range. This is with three tanks and a spear and a scooter. When I first started diving this configuration my consumption went up to around .53. I have done 340 hours underwater since Christmas so it has really come down as a result. I will leave my response at .4-.49. Thanks for the poll.
 
RayfromTX:
As I have gotten more experience my air consumption has continued to drop and I now have quite a few dives that are in the .38 range. This is with three tanks and a spear and a scooter. When I first started diving this configuration my consumption went up to around .53. I have done 340 hours underwater since Christmas so it has really come down as a result. I will leave my response at .4-.49. Thanks for the poll.
Click to expand...
That is a really significant improvement, a good example of the effect of experience, with a change in equipment or with diving in general
 
I just discovered a big problem in my gas consumption numbers. I have had my logging software set to the wrong size tank this whole time. This makes a lot of sense because every time I do a running calculation on the fly while diving my consumption always seems to be less than the software tells me later. Today my wife told me what her consumption was and it made no sense. I started with less gas, ended with more gas and had a slightly deeper average depth. As I dug a little deeper I discovered that I had it set to LP85(13 liters) which is what I dive at home. Here I dive AL80s which are 11.1 liters. My gas consumption on todays dive was .346 Cuft per minute. The better dives are about .32 and the worse dives where I work a lot are .39 so I guess I will change my response because it appears that I am always under .4 cuft per minute. This makes sense because we used just over 3/4 of a tank on a 2 hour and 10 minute dive with an average depth of 20 feet and yesterday I did a solo dive for 4 hours and 10 minutes at an average depth of 35 feet and used 2 1/3 al80s.

I'm pretty pleased.
 
Hi @RayfromTX

I'm not at all surprised after all of your diving in Cozumel and the relaxed description, way to go. I have my RMV for 1553 of my last 1570 dives, all conditions, and my average RMV is 0.36 cu ft/min with a std deviation of 0.04. So 95% of my dives are between 0.28 and 0.44 cu ft/mn. One's RMV is very useful for gas planning.

It would be interesting to know how your RMV has changed over time. I did not start checking my RMV until 443 dives, my gas consumption was already pretty much set with minimal decrease and less variability since then.
 
It used to be .53 or so at the beginning of a trip and around .43 at the end of a trip if just drift diving a single tank. It was higher when I started diving three tanks and kicking in cold water. Now I'm kicking less as I use a scooter and I'm diving a 7mil here in Coz with temps in the mid to low 80s because warmth uses less gas. I do still fin for stability and when I'm exploring a reef or a wall I'm not using a scooter so I'm kicking three tanks and a scooter and sometimes a camera too but at least I'm not kicking to get from point a to point b.

Sounds like we are using about the same amount of gas now. Most of the people that I know that use that amount are petite women. Cameron used even less than that. I remember a shore dive we did one new years day. He had a shorty with 2,200 psi to start and we dove for 90 minutes on it. He was pushing a big effing camera rig too and using some silly fins someone had asked him to try out that looked like venetian blinds. He always amazed me. I miss him terribly.
 
RayfromTX:
It used to be .53 or so at the beginning of a trip and around .43 at the end of a trip if just drift diving a single tank. It was higher when I started diving three tanks and kicking in cold water. Now I'm kicking less as I use a scooter and I'm diving a 7mil here in Coz with temps in the mid to low 80s because warmth uses less gas. I do still fin for stability and when I'm exploring a reef or a wall I'm not using a scooter so I'm kicking three tanks and a scooter and sometimes a camera too but at least I'm not kicking to get from point a to point b.

Sounds like we are using about the same amount of gas now. Most of the people that I know that use that amount are petite women. Cameron used even less than that. I remember a shore dive we did one new years day. He had a shorty with 2,200 psi to start and we dove for 90 minutes on it. He was pushing a big effing camera rig too and using some silly fins someone had asked him to try out that looked like venetian blinds. He always amazed me. I miss him terribly.
Click to expand...
Those fins were experiment ones, and I’ve heard of them. Apparently, they are very efficient.

SeaRat
 
I'm not sure if this helps me have a low SAC rate average but my wife bought a device. Top is supposed to be blood oxygen level and you are supposed to be at 95% or above. Below is heart beats per minute.

She thinks I will soon be a zombie. This taken when I am at work in my office.

2688.jpg
 
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