Air Consumption Rates

[Gac]

Hey guys. I was just putsing around in a quarry this past weekend and had a great time. I am still pretty new to SCUBA (been snorkling for a few years), and I'm working on improving my air consumption. I dove with 3 other people, one of whom has been diving regularly for several years. We all started at around 3000psi on AL80's. The first two guys bugged out after 40 minutes. The other guy and I lasted an hour. I had 800psi left after 1 hour down (to his 350, :14: ). Our max depth was 35 feet and averageed about 25-30.

Is this a good rate of consumption? What kind of consumptions rates are you guys getting?

 

[teknitroxdiver]

You can't really call good or bad on SAC rates (that's what they call this stuff...Surface Air Consumption rate).

It depends on your experience and your physical characteristics. For example I could stay at 30 feet for 1:10 with 1000 PSI in reserve (an AL80 starting at 3000). Another person might only be able to stay 40 minutes, or might last 2 hours.

 

[Mo2vation]

Hey guys. I was just putsing around in a quarry this past weekend and had a great time. I am still pretty new to SCUBA (been snorkling for a few years), and I'm working on improving my air consumption. I dove with 3 other people, one of whom has been diving regularly for several years. We all started at around 3000psi on AL80's. The first two guys bugged out after 40 minutes. The other guy and I lasted an hour. I had 800psi left after 1 hour down (to his 350, :14: ). Our max depth was 35 feet and averageed about 25-30.

Is this a good rate of consumption? What kind of consumptions rates are you guys getting?

First off, welcome to the board.

Your gas consumption rates are dependant on a lot of things:

* How hard you're working (kicking fast, drifting, current, etc.)

* Equipment (streamlined or stuff hanging all over the place, weighting, etc.)

* Dive profile (depth timing, etc.)

* Dive Skills (are you a stand up diver, do you swim like a fish, are you efficient in the water, etc.)

* Temperature (is the water cold... are YOU cold?)

* Mood (are you relaxed, nervous, excited, concerned, etc.)

* Experience (new and full of wanderlust, experienced and kicking back, etc.)

The only real thing you can count on is this: The more you dive, the "better" your consumption rate will be... the tank you're diving today will last longer under similiar circumstances a year from now.

Usually.

Consumption and the quest for "good consumption" always makes me smile. I used to watch this so closely - like it was a measure of a good dive or a measure of me as a good diver... coming home, calculating my SAC, downloading my dives immediately and checking, etc.

While I believe its important to know your working and resting rates (for planning purposes) I think its also important to say that this isn't a contest, and consumption is relative.

For example - its just as important to know how my consumption rates to my regular buddy's rate... so I "know" about where they are with their supply, and vice versa along the dive. This contributes to my peace of mind and actually helps me relax. Driving my consumption down, etc.

A lot of things contribute. IMO, the largest impact will be experience. Sounds like you're off to a good start - don't get a headache from breathing too infrequently (like I used to.... :11: )

Others will chime in. I'll stop now.

Welcome to the board. Keep asking questions.

---
Ken

 

[spectrum]

Hey guys. I was just putsing around in a quarry this past weekend and had a great time. I am still pretty new to SCUBA (been snorkling for a few years), and I'm working on improving my air consumption. I dove with 3 other people, one of whom has been diving regularly for several years. We all started at around 3000psi on AL80's. The first two guys bugged out after 40 minutes. The other guy and I lasted an hour. I had 800psi left after 1 hour down (to his 350, :14: ). Our max depth was 35 feet and averageed about 25-30.

Is this a good rate of consumption? What kind of consumptions rates are you guys getting?

First heed what others have posted. It's all dependent on the details of the dive, the diver, the day and the gear etc, etc.

To answer your question I took your numbers and used an average depth of 27 feet and came up with a SAC rate of .51. It assumes a perfect 27 foot average. Only with a computer or a truly controlled time at depth test can you get a true value.If you go back into the archives you can find polls that atempt to show a cross section of SAC rates, probably skewed to the wliling posters of lower values. I think you will find you compare quite nicely as a new diver. But this is only a snap shot.

In the circle of new divers that I have been hanging with I have been blessed with relativey low air consumption but I have had dives where the situation caused me to consume much more than my norm. My wife is closing the gap on consumption but is not that comfortable with night and dark quarry dives and on those she rips right through the air. Same everything except situation and it all changes.

Just be the best diver you can be and someday we can be good mentors, that's my goal. Just dive, dive and dive.

Pete

 

[teknitroxdiver]

Yeah I forgot to mention the effect of dive conditions. That can have a massive impact, more than anything else. For example, one one drift where I barely raised a finger I got about .38. On a deeper wreck with a massive current it was up to about .72.

 

[TSandM]

What I got out of the great gas management seminar that NW Grateful Diver did for us last week: If you know your RMV (gas consumption in cubic feet), it can help you plan dives that you know you can complete safely, and help you assess the reserves you need for emergencies if they occur during a given dive. If you know your SAC (gas consumption in psi), you can more intelligently plan your dive, including your turn pressure.

As everybody else has said, all these numbers will vary with conditions, with mental state, with experience, and with task loading. Watching trends can be useful -- do you tend to use air faster when diving in certain places, or under certain conditions, or with certain people? Is your air consumption improving with experience and/or training?

There is no good or bad. There are data, and they are useful in doing intelligent planning.

 

[stevetim]

Being an average sized male @ 5'10" and 170lbs., over the course of about 12 dives I have almost halved my air consumption per dive. My dives start at 3000psi and end on surface at 500psi. On my first 60 ft. post-cert. dive, I could stay down for only about 35 minutes due to wasted movements, constant buoyancy fiddling, and just plain upaced breathing. On my last few dives I can stay at 60ft. for about 50 minutes, do my ascent, safety stop for 3m @ 15ft., and still have about 750psi to spare. And that is from a total newb diver.

Just take everyone's advice(I love seeing 0-15 dives divers give such expert advice ) and practice. I now keep pace with my buddy's wife who is 5'5 @ 110lbs. It really feels good to not ruin others' bottom time, that's the biggest reward to me.

About my personal consumptions @ 25-30 ft., I get an average of 80 minutes. Longest is 95 in that depth range( I did push a hair under 500psi).

 

[Mo2vation]

I now keep pace with my buddy's wife who is 5'5 @ 110lbs. It really feels good to not ruin others' bottom time, that's the biggest reward to me.

She uses an HP100, and I dive the Waterheater.

That's MY strategy! Be a hoover (well, maybe more of a Dirt Devil... ) and just carry more gas!

---
Ken

 

[stevetim]

She uses an HP100, and I dive the Waterheater.

That's MY strategy! Be a hoover (well, maybe more of a Dirt Devil... ) and just carry more gas!

---
Ken

More gas... :11ztongue mmmm. Steel 100's or more in the future for sure.

 

[The Kraken]

Well, Gac,
Based upon the data you supply, and given that you were diving an aluminum 80 at a fill pressure of 3000 psi, your SAC calculates out to be .45 cfm.

I'd have to say that's a pretty good SAC.

the K