So how long does AL80 last?

[herman]

Damn so I have a lot to do.
Also why do we consume more i coldwater?

Because your body has to burn fuel to keep warm and burning fuel requires oxygen, the wetsuit or drysuit create more drag you have to move and the extra weight needed to submerge the wet/dry suit you have to expend more energy to move the extra mass.

 

[TSandM]

I've never heard a good explanation for why gas consumption is higher in cold water, and mine isn't by very much. You could argue that you're probably putting more air in a BC in cold water, since you have more buoyancy loss from your exposure protection to compensate for, but unless you are see-sawing a lot, that really shouldn't be significant. Obviously, if you are shivering, you're in essence exercising, and you will use gas a lot faster -- but you shouldn't be staying in the water until you shiver. And if you swim to stay warm, you'll use gas faster, too. But if you're doing the same amount of physical work, you should have the same gas consumption.

Edited to add: People often refer to the energy being "burned" to stay warm. In fact, the body has no ability to change its metabolic rate acutely like that, which is why we shiver. Shivering is the body's one way to generate more heat; all the other adaptive mechanisms for cold are related to trying to conserve the heat you already have.

 

[Aqua-Andy]

I think the best advice is "don't worry about it, go dive, have fun". Your air consumption will come down over time.

 

[Splitlip]

Mine lasts for months. But then I only use it for blowing out the AC condensate line.

 

[RonFrank]

There is one thing you can do to dramatically improve you air consumption.... stop breathing!

Seriously, slow deliberate movements, keep you hands still, work on hovering. You want to be still and practice that. You should not have to move, just hover without kicking or moving. You may not be able to do this at first but work on it every dive. At some point being motionless will become natural, and then you will be one with the sea grasshopper.... well ok nuff zen junk, but seriously try to be motionless for 5 minutes on each dive.

 

[DivemasterDennis]

I'm with AquaAndy on this one. Go dive, have fun, and monitor your gauges. Air consumption invariably slows with experience and competence, though there will always be huge variations from one person to the next. Here are some useful tips for improving air consumption:
1. Be properly weighted. Over- or under- weighting will cause you to have to move more during a dive to maintain buoyancy. You will also be adding and releasing air from your bc more often, thus depleting your air more quickly.
2. Trim you buoyancy often. If you are fining or kicking to maintain depth, you need to adjust your BC accordingly.
3. Move less. Many new divers "run around" during a dive. Slow down, enjoy the view and experience, and you will use less air.
4. Find a place and park your hands and arms when not needed to point or take a photo. Hands clasped at the waist is a popular position. You don't need to swim with your arms.
5. Streamline your equipment. Part of that is proper weighting so you aren't pushing a full BC through the water. Also, attach your alternate air source, gauges, and any other equipment so that is secure in close proximity to your body.
6. Stop thinking about it. Whether good science or not, my experience is that people preoccupied with air consumption actually consume more- perhaps due to stress. JUst relax, but do casually check your gauges regularly.
So as Aqua Andy said- Dive- have fun! It's not a contest.
DivemasterDennis

 

[farsidefan1]

One thing on propulsion through water. Often I see newer divers constantly kicking, even when they are not trying to move. They just kick to stabilize. First get your trim in order then kick - coast- kick-coast. After each kick DON'T MOVE YOUR FINS till you drift to a stop.

 

[Charlie99]

I've never heard a good explanation for why gas consumption is higher in cold water, and mine isn't by very much.

. I notice that I consume more air when chilled. I assume the body increases metabolism to keep the core temp up, thereby indirectly increasing air consumption.

 

[TSandM]

No, the interesting thing is that the body has no way to increase metabolism acutely, other than increasing muscle activity, which is why we shiver. We conserve heat by constricting surface blood vessels and pooling blood in the deeper tissues, but metabolism is whatever it is. That's why swimming harder keeps you warm longer.

 

[Edward3c]

I've had a few dives now with just myself and my buddy straight out of OW about 6 weeks ago. All our dives so far have been with a single al 80 usually at a depth of around 6-9 meters with a max depth of around 15m, but we stay around 8 meters or so.
We start our dive with about 200-220 bar and the dive lasts about 35-40 minutes and we return with 20 bar or so.
Does this sound right in terms of consumption because I see many other people here and there saying they can last longer than an hour with one tank. Maybe I am consuming too much air.

For our level of experience you dive times are not unusual.

Did your instructor teach you to finish dives with such a low cylinder pressure (20Bar)? My students (I teach the BSAC syllabus) are taught to use the Rule of thirds - one third out, one third back, one third reserve. Therefore dives finsh and you leave the water with about 70Bar (for a 232Bar cylinder).