Air consumption rates.

[scubadada]

Have you tried measuring your RMV sitting on the sofa watching (unexciting) tv?

You are saying that your air consumption can be as low as that of a 10 year old child sitting watching TV. Maybe I will incentivise him in a future experiment - "you can watch to until you run of gas..." sort of thing.

Low air consumption seems to be a major form of willy waving here. It would be interesting to know what average competent divers manage. My typical warm blue water dives are more like 15l/m. I know that under stress (failing to perform a shutdown for example) it can hit 35l/minute or more.

Why would I measure my RMV watching TV if my computer captures my gas consumption, average depth, and dive time, and then calculates my RMV on every dive? The download software uses a default cylinder for the calculation, but can be changed to any cylinder you might be using. The diving RMV is extremely useful in gas planning. I have learned a considerable amount regarding the variables that affect my own gas consumption by following my RMV over the last 6 years.

 

[KenGordon]

Why would I measure my RMV watching TV if my computer captures my gas consumption, average depth, and dive time, and then calculates my RMV on every dive? The download software uses a default cylinder for the calculation, but can be changed to any cylinder you might be using. The diving RMV is extremely useful in gas planning. I have learned a considerable amount regarding the variables that affect my own gas consumption by following my RMV over the last 6 years.

As a baseline. It seems unlikely you'd ever use less than that, then anything worse is bcd, worry and find fiddling too much

 

[scubadada]

As a baseline. It seems unlikely you'd ever use less than that, then anything worse is bcd, worry and find fiddling too much

Hi Ken,

I understand your comment now. My breathing pattern is quite different diving than it is on the surface. I'd rather know the range of RMVs I have underwater. My lowest diving RMV is 0.28, I've only been under 0.3 a few times, that's probably the lowest I will ever be and is a good baseline. This was an effortless, solo, warm water drift. My reliable average is 0.37, I use 0.75 for contingency gas planning like my redundant air source for solo diving. The highest RMV I've had for a whole dive is 0.63, that was a very cold, deep, dark, wreck dive with significant effort.

Good diving, Craig

 

[uncfnp]

On this board it seems common to see claims of surface equivalent air consumption (SAC or RMV depending on who you ask) of the order or 0.3 cuft/minute or about 9l/minute.

I have previously measured by own rate sat on the sofa and get something between 9 and 10 l/minute. My lowest whole dive rate is about 12 l/minute (0.4 cuft/minute) on totally easy warm water dives with no current. Almost always it is higher than this.

Maybe those claiming 0.3 cuft/minute are younger and fitter than me, so I found a 10 year old and forced him to watch cartoons while breathing from a 3l cylinder. His rate came out at 8 l/minute.

This talk by a well respected diving doctor and researcher,


talks about ventilation and in particular co2. it covers technical diving but the breathing and co2 aspects apply at moderate depth too.

I leave it for those watching to form an opinion about trying to breath less.

Ok Ken. Got varification. On a boat dive today. There was a guy, just average and by that not especially old, young nor athletic. Diving for about a year. Had a steel 120. Dive was 92 minutes. I can't give exact average depth for him but mine was 40 feet and he was probably somewhere close. He finished with 1700 psi. Independently varified. I calculate that as .29 so it can be done. And apparantly this is not unusual. He barely moved.

Me? I'd rather swim over to look at that fish.

 

[Neilwood]

Ok Ken. Got varification. On a boat dive today. There was a guy, just average and by that not especially old, young nor athletic. Diving for about a year. Had a steel 120. Dive was 92 minutes. I can't give exact average depth for him but mine was 40 feet and he was probably somewhere close. He finished with 1700 psi. Independently varified. I calculate that as .29 so it can be done. And apparantly this is not unusual. He barely moved.

Me? I'd rather swim over to look at that fish.

Likewise - I am down there to look at all the life there so there seems no point to me hovering in one point hoping things come to me. I would rather get 46 minutes of swimming about than 92 minutes of hovering.

 

[jstrang]

On a boat dive today. There was a guy, just average and by that not especially old, young nor athletic. Diving for about a year. Had a steel 120. Dive was 92 minutes. I can't give exact average depth for him but mine was 40 feet and he was probably somewhere close. He finished with 1700 psi. Independently varified. I calculate that as .29 so it can be done.

Unless he was in a LP steel 120 - then his Sac 'jumps' to 0.4

Personally it doesn't matter how good my Sac is - my wife's is always 30% better. Warm water easy dives in the Caribbean I get 0.4 - she gets 0.28 - cold water wrecks I get 0.55 - she get 0.4.
The only exception is if she lugs around a BIG camera with strobes, into a strong current, and I take off on her...

 

[uncfnp]

Unless he was in a LP steel 120 - then his Sac 'jumps' to 0.4

Personally it doesn't matter how good my Sac is - my wife's is always 30% better. Warm water easy dives in the Caribbean I get 0.4 - she gets 0.28 - cold water wrecks I get 0.55 - she get 0.4.
The only exception is if she lugs around a BIG camera with strobes, into a strong current, and I take off on her...

Nope. It was a HP 120.

And that's why guys with female dive partners often dive the larger tanks but this just shows it can be done and by the guys.

 

[Akimbo]

... He finished with 1700 psi. Independently varified. I calculate that as .29 so it can be done. And apparantly this is not unusual. He barely moved.

Me? I'd rather swim over to look at that fish.

I concur. Perhaps a more important question is: Is it better to climb the ladder with most of your gas or less CO2 in your blood stream?

Doing both is fine, but less CO2 is better. Relaxed and comfortable in the water is an excellent goal for everyone but artificially lowering gas consumption below optimum ventilation requirements is ill-advised.

 

[MXGratefulDiver]

... where else but in scuba diving can you listen to a bunch of old men sitting around bragging about how low their SAC is ...

... Bob (Grateful Diver)

 

[Rhone Man]

On this board it seems common to see claims of surface equivalent air consumption (SAC or RMV depending on who you ask) of the order or 0.3 cuft/minute or about 9l/minute.

0.3 cu ft/min is a pretty extraordinary SAC, even in very benign conditions. I consider myself in the top couple of percentile points when it comes to gas consumption, and on my best, best day I can do 0.38 (according to my Suunto). Someone who can consistently do a full 25% better than that would be a very special (and very small) diver.