Air Consumption
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beester
Contributor
First of all don't worry too much about gas consumption (SAC), it gets better with experience. No use to compare to other people (even of similar body size) because there are too much variables at play and you might get stressed and focus too much on something that in reality is not so important.
What is important is that you always make sure that you have sufficient air/gas to make the dive and incorporate this in your dive planning.
So that out of the way how can you improve your air/gas consumption? A couple of pointers, breaking down some things that can affect your consumption rate:
- temperature of the water: Has a big impact on your consumption, specially if you feel cold. Your body reacts by increasing your metabolism, to increase your internal stove, which of course needs fuel, mainly oxygen. You can compensate by wearing sufficient isolation (drysuit, whatnot) but even then... if you compare a tropical dive vs a cold water dive your SAC will be higher in cold water.
- Weight and your weighing underwater: If you are overweighted (which many newer divers are) this will impact your SAC. How? You are constantly compensating for this weight by using your bcd/wing. Meaning there is more air in your bcd that you need to manage (deflate when you rise a bit, inflate again when you drop down a bit) over a 1 hour dive this adds up. So the less (over)weight you are, the smaller the gas bubble you need to manage in your bcd, the lesser the SAC.
- Position in the water: If you just keep a float underwater, in equilibrium (neutral buoyancy) depending on your BCD/wing your position in the water will be different. With most BCD's it will be more vertical than horizontal. Which means that while diving you are presenting a bigger surface for water to push against while moving forward. Meaning you have to push harder to move, increasing your SAC.
- Activity level underwater: The less you move, the less "active" you are, the lower your SAC. Also if you move more efficient, your SAC will lower (think different ways of finning/propulsion). Finally for sure if you are moving against current your SAC will increase, if you are "fast" underwater your SAC increases... etc
- Breathing rate: You should be aware of your breathing rate underwater. By all means don't skipbreath (holding your breath), but slowing down your breathing, focussing on exhaling rather than inhaling, and being aware of your breathing rate will have a positive impact on your SAC.
- First moments in the water: The first few minutes of the dive impact your SAC very much. Most divers are still a bit exerted from putting all their gear on, quick equipment check, jumping in the water from the boat or even more so when shore diving (walking in the water), then when they are still catching their breath they start the dive, overbreathing the first few minutes of the dive. If possible just take a few minutes in the water before starting your dive, you no longer feel the weight of your equipment and you can relax. Use these minutes to do a final check of the diveplan/brief... and then when everybody is relaxed start the dive. This will have a big impact on SAC, because the first 5-10 minutes are already relax vs overbreathing.
- Stress: If you are taskloaded or stressed in any way, your breathing rate will increase, and your SAC will suffer. The only thing you can do is realize this and work at the trigger of the stress (gain more experience).
Hope this helps.
B
-
What is important is that you always make sure that you have sufficient air/gas to make the dive and incorporate this in your dive planning.
So that out of the way how can you improve your air/gas consumption? A couple of pointers, breaking down some things that can affect your consumption rate:
- temperature of the water: Has a big impact on your consumption, specially if you feel cold. Your body reacts by increasing your metabolism, to increase your internal stove, which of course needs fuel, mainly oxygen. You can compensate by wearing sufficient isolation (drysuit, whatnot) but even then... if you compare a tropical dive vs a cold water dive your SAC will be higher in cold water.
- Weight and your weighing underwater: If you are overweighted (which many newer divers are) this will impact your SAC. How? You are constantly compensating for this weight by using your bcd/wing. Meaning there is more air in your bcd that you need to manage (deflate when you rise a bit, inflate again when you drop down a bit) over a 1 hour dive this adds up. So the less (over)weight you are, the smaller the gas bubble you need to manage in your bcd, the lesser the SAC.
- Position in the water: If you just keep a float underwater, in equilibrium (neutral buoyancy) depending on your BCD/wing your position in the water will be different. With most BCD's it will be more vertical than horizontal. Which means that while diving you are presenting a bigger surface for water to push against while moving forward. Meaning you have to push harder to move, increasing your SAC.
- Activity level underwater: The less you move, the less "active" you are, the lower your SAC. Also if you move more efficient, your SAC will lower (think different ways of finning/propulsion). Finally for sure if you are moving against current your SAC will increase, if you are "fast" underwater your SAC increases... etc
- Breathing rate: You should be aware of your breathing rate underwater. By all means don't skipbreath (holding your breath), but slowing down your breathing, focussing on exhaling rather than inhaling, and being aware of your breathing rate will have a positive impact on your SAC.
- First moments in the water: The first few minutes of the dive impact your SAC very much. Most divers are still a bit exerted from putting all their gear on, quick equipment check, jumping in the water from the boat or even more so when shore diving (walking in the water), then when they are still catching their breath they start the dive, overbreathing the first few minutes of the dive. If possible just take a few minutes in the water before starting your dive, you no longer feel the weight of your equipment and you can relax. Use these minutes to do a final check of the diveplan/brief... and then when everybody is relaxed start the dive. This will have a big impact on SAC, because the first 5-10 minutes are already relax vs overbreathing.
- Stress: If you are taskloaded or stressed in any way, your breathing rate will increase, and your SAC will suffer. The only thing you can do is realize this and work at the trigger of the stress (gain more experience).
Hope this helps.
B
-
beester
Contributor
KatieMac
Contributor
Not necessarily. Again, there are lots of factors. But I was never over .5.@scubadada Thank-you, I'll assume the newer divers were on the right of the graph and I am normal.
When I started diving and in particular during a liveaboard trip, I got quite obsessed by my air consumption as I was needing to finish dives early on occasion. The more I obsessed the worse it became. Once I got properly relaxed, it got better on its own.
I am quite a big guy 6'3 with more padding than I should have so I have accepted that on trips, I rent a 15L when everyone else is using a 12L.
I am quite a big guy 6'3 with more padding than I should have so I have accepted that on trips, I rent a 15L when everyone else is using a 12L.
0321tony
Registered
I'm 5'10 and 215 lbs I dive primarily cold water with a drysuit my RMV rate runs about .50 - .60 if I am using a DPV and just enjoying the ride it goes down to about .45 - .50. I have never checked mine in warm water.
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DBPacific
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You'll get better and more comfortable as time goes on, just focus on improving buoyancy, trim, and your comfort level and have fun.
I only ever calculated SAC rate (and tired brain isn't currently remembering how different SAC and RMV are). But I think my current SAC rates for warm water is about 0.2-0.3 and cold I typically run 0.45-0.5. I'm a small 5'3" though and I rarely get cold in the water.
I only ever calculated SAC rate (and tired brain isn't currently remembering how different SAC and RMV are). But I think my current SAC rates for warm water is about 0.2-0.3 and cold I typically run 0.45-0.5. I'm a small 5'3" though and I rarely get cold in the water.
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