Average Gas Consumption

[Kimela]

No problem with your ears too?

No problem with ears. Occasionally I have to hesitate on the initial descent - not nearly as much as my husband. Never any problems after a dive (hope I didn't just jinx it).

 

[Kimela]

They are stupid because the purpose of the safety stop is to help you off gas....that means light movement, not heavy rushing about.

Hadn't thought about that. Sounds like I'm being told not to 'play around'. I stay within 10 to 25 ft (I think 25ft is the outside of my depth on my Peregrine for the safety stop). The only drawback I've seen in my 'stupid' stuff is running low on air. Not exactly a 'problem' in my books.

 

[dumpsterpurrs]

Idea for folks on the ultra-low end of SAC: Try switching to smaller cylinders on shallower dives and watch your SAC rates drop further! I was diving in fairly strong full moon currents in Puerto Galera, and consistently ended the 55 to 60-min dives with around 100-120 bar when others got 40-70, so I decided to switch from the regular 11.1L AL80 cylinders to the baby 7.1L cylinders for the afternoon and night muck dives. My SAC immediately went from around 7.5-8L/min down to around 6.5L/min. I could still comfortably end with around 80-100bar (equivalent to 50-65bar of 11.1L) on those dives. The baby bottles feel a lot more comfortable underwater, especially for a shorter person like me.

 

[scubadada]

Hi @dumpsterpurrs

You're not kidding about the ultra-low end. Your starting RMV was 0.26-0.28 cu ft/min and fell to 0.23 cu ft/min when you switched to the smaller tank (sorry, converted for those of us using imperial units ). I hope you are represented in the lowest RMV category in the poll, if not, please vote.

I may try your small cylinder suggestion next time my wife and I visit Bonaire. Dive Friends has plenty of 63 cu ft cylinders available.

 

[rsingler]

Physiologically speaking, and dependent upon body mass, if you accept that there is no magical drug that truly decreases your metabolic rate, any 70kg male who claims a SAC below 0.23 CFM is almost certainly slightly, if not significantly, hypercarbic.
Unless the dive was, start to finish, a Zen drift dive in 80° water requiring zero movement.

And for those with great consumption on an average low effort dive, you shouldn't even try for less than 0.35 CFM. The required breathing habit (and baseline hypercarbia) will not put you in a good place on a deep dive where you're suddenly required to work with high gas density.
Jes' sayin'.

Diving Doc

 

[scubadada]

Good points by @rsingler

I have always had very good gas consumption, perhaps related to having been competitive swimmer for many years. Whatever, I have 2,350 dives and have my RMV for 1,877 of those dives since 2010. My average RMV over a very diverse collection of dives is O.36 cu ft or 10.2 l/min. I have only 17 dives with an RMV <0.28 cu ft or 7.9 l/min with 1 at 0.26 and 4 at 0.27 cu ft/min.

All of these low gas consumption dives were extremely easy, nearly effortless dives in warm water, 10 in Bonaire, 6 in SE Florida, and 1 in Roatan. I am quite sure that these dives represent my own lower limit for gas consumption with the easiest of diving.

EDIT: @dumpsterpurrs is a petite woman, experienced diver. I can easily see her with the gas consumption she posted. The comment by @rsingler specifically mentions a 70 kg man.

 

[scubadada]

Wow, very quick, another 1,000 views, now more than 59,000. Another 10 votes in the poll, now 776.

The median, mode, and weighted average remain 0.5-0.59 cu ft/min or 14.2-16.9 l/min

If you have not voted in the poll, please consider doing so. If your average RMV has changed, please change your vote.

Good diving to all

 

[WillieJustice]

If math isn't your strong point, there are plenty of specialized calculators on the internet, for example Surface Air Consumption Calculator | DiveBuddy.com.
FYI, assuming you ended with 2500 psi on your four dives you posted, you are solidly in the 0.6-0.7 cuft/min camp.

I did that calculation, and that's exactly where I am.

 

[WillieJustice]

Physiologically speaking, and dependent upon body mass, if you accept that there is no magical drug that truly decreases your metabolic rate, any 70kg male who claims a SAC below 0.23 CFM is almost certainly slightly, if not significantly, hypercarbic.
Unless the dive was, start to finish, a Zen drift dive in 80° water requiring zero movement.

And for those with great consumption on an average low effort dive, you shouldn't even try for less than 0.35 CFM. The required breathing habit (and baseline hypercarbia) will not put you in a good place on a deep dive where you're suddenly required to work with high gas density.
Jes' sayin'.

Diving Doc

And I'm an approximately 88kg man with a fairly low fat mass for my size and age. So, I burn through air, especially if I'm doing a bit of work on the dive, like cold water and moving a fair amount.

 

[Belzelbub]

And I'm an approximately 88kg man with a fairly low fat mass for my size and age. So, I burn through air, especially if I'm doing a bit of work on the dive, like cold water and moving a fair amount.

All of that will make a significant difference. Dives where I'm not doing a whole lot, and am warm, my SAC drops pretty low. If I'm working, it could easily be double or more what a resting dive would be.