Air Consumption

[EireDiver606]

It’s called gas consumption not air consumption, your consumption doesn’t suddenly change if you’re not breathing air.

It depends how relaxed you are. You could be very comfortable in the water but if you’re overthinking everything and are having issues with buoyancy your consumption will increase because you’re slightly stressed.

Also, if I’m diving with an unknown diver who I don’t know how he behaves underwater, subconsciously my surface consumption rate increases very slightly I feel.

The best way to improve it is to just dive, while actively focusing on buoyancy and trim and proper propulsion techniques. Even if you’re a good diver, it could still take time to improve.


I have a question : if you have more muscle on your frame, does that increase your consumption rate (whether it’s neglible or not?). Participating in cardiovascular exercise will help you’re breathing rate and ability to minimize negative breathing reactions to incidents or stress underwater ie react better.

 

[uncfnp]

What's a good SAC

I think @scubadada has a survey too but I couldn’t find it.

 

[scubadada]

Hi @HKGuns

Here are the pooled results from 2 SB polls, one from 2009 and one from 2016. The question was, what is your average RMV? There were 339 total respondents. RMV is in cubic feet/min. There are many caveats to interpreting polls done on SB. This summary has previously been posted, including in the thread referenced by @uncfnp. There have been numerous threads discussing gas consumption over the years

 

[HKGuns]

@scubadada Thank-you, I'll assume the newer divers were on the right of the graph and I am normal.

 

[nolatom]

You're looking for a conservative number? Look at the RMV chart from Scubadada above.
My personal experience was about .7 cubic feet per minute on the surface as a new diver, improving to .6 and maybe .5 And this depends on conditions, as you've heard. Warm, no current or a drift dive, familiar venue, not too deep, nice vis, nothing scary? You'll sip gas. Cold, dark, deep, spooky, rippin current and you have to find the boat at the end (where's the friggin boat?? Huff huff)? You'll gulp air-- watch your pressure gauge like a hawk and don't stray too far.

 

[scubadada]

@scubadada Thank-you, I'll assume the newer divers were on the right of the graph and I am normal.

I doubt the polls accurately reflect the general diving population. The respondents are members of SB, know their average RMV, and respond to a poll on the topic. However, I do think the middle of the curve from 0.4-0.59 probably does reflect the average RMV of the majority of established divers.

I did not start measuring my RMV until I had nearly 500 dives. My RMV has improved only a little over the next 1350 dives. I think I'm at my setpoint.

 

[rhwestfall]

@scubadada Thank-you, I'll assume the newer divers were on the right of the graph and I am normal.

Define "normal"

Put me in 36 degree dark water, dry suit, Doubles, Stages, rough conditions, camera.... I will be around 1.0 ......

Put me in the Niagara River (3 kt current) to just go for a ride, and I will be 0.5 - 0.6

Put me in Curacao on a reef, and I will be 0.4 - 0.5

YMMV

 

[mcpowell]

I’m 5’9” 190 lbs. My average SAC (per my Teric) is .30-.35. This is for easy drift dives in Cozumel, light current in the FL Keys, or no current dives in a FL spring. My son and I had a “sporty” drift dive where the current kicked up with a bit of turbulence last year, the divers got spread out a bit at the end of the dive (think washing machine) and I had to think about staying calm a couple of times. We were never in trouble, but I was challenged to hold our safety stop depth. My SAC was .42 on that dive. I haven’t had a dive where I really felt “in trouble” so I don’t know what it would be then.

I try to run through my computer display just after I level off after our initial descent. My SAC typically starts higher and then levels out as the dive progresses. I think it’s from the initial excitement and effort of getting in the water.

 

[happy-diver]

I'm older with average air consumption on an Al80
and I get an above average increase on a steel 120
but when I add my steel 25 pony which I never ever
use in plan calcs, my consumption becomes brilliant!


and I never ever use my air filled pony as a dive extender

 

[BRT]

I’m 5’9” 190 lbs. My average SAC (per my Teric) is .30-.35. This is for easy drift dives in Cozumel, light current in the FL Keys, or no current dives in a FL spring. My son and I had a “sporty” drift dive where the current kicked up with a bit of turbulence last year, the divers got spread out a bit at the end of the dive (think washing machine) and I had to think about staying calm a couple of times. We were never in trouble, but I was challenged to hold our safety stop depth. My SAC was .42 on that dive. I haven’t had a dive where I really felt “in trouble” so I don’t know what it would be then.

I try to run through my computer display just after I level off after our initial descent. My SAC typically starts higher and then levels out as the dive progresses. I think it’s from the initial excitement and effort of getting in the water.

Might also be that your tank was hotter than the water you are diving in.