Air Consumption

[SteveDiver]

In reviewing my air consumption I have noticed that I use less air on my deep dives which is the first dive. On the second dive (shallow) I use more air. Bottom times are very close to being the same. This does not make sense to me. I would think that it would be the other way around. Can anyone enlighten me?

 

[Quarrior]

In reviewing my air consumption I have noticed that I use less air on my deep dives which is the first dive. On the second dive (shallow) I use more air. Bottom times are very close to being the same. This does not make sense to me. I would think that it would be the other way around. Can anyone enlighten me?

My thoughts on it are that on a deep dive you are spending time sinking, rather than swiming. On the ascent you let your bouyancy bring you up slowly, rather than swimming. Consequently, you are doing less work on a deep dive.

Shallow dives you end up with a short sink time, long swim time, and short ascent.

 

[SteveDiver]

OIC makes sense to me... Thanks..

 

[DepartureDiver]

Interesting ... I asume you are talking about total gas used ... perhaps you are swimming around more on your shallow dive.

 

[String]

Shallow dives here often involve more swell, surge, current etc so are normally more strenuous. I sometimes find my air consumption higher than my average SAC on dives <10m or so for this reason.

 

[pt40fathoms]

Well, I must say that the prospect of a higher sac rate for shallow dives has never occured to me. However, based on the rational made here to explain this, it makes sense.

I guess old dogs really can learn new tricks. :11:

 

[O2BBubbleFree]

Could it also be that your using more air because it's the second dive (maybe a little tired), irregardless of depth?

 

[String]

Slight point, if your PADI/NAUI or whatever SAC means the same as ours, ie SURFACE air consumption its designed to factor out depth changes and give you a consumption as it would be at the surface.

Technically ignoring other factors such as exertion, lower in deco stops etc youd expect the same ballpark figure regardless of depth.

 

[Diver0001]

In reviewing my air consumption I have noticed that I use less air on my deep dives which is the first dive. On the second dive (shallow) I use more air. Bottom times are very close to being the same. This does not make sense to me. I would think that it would be the other way around. Can anyone enlighten me?

How do you measure your air consumption?

R..

 

[Mako Mark]

cold could be a factor too, you breathe faster when you are cold, and you are probably colder on your second dive..

I have also heard people say that nitrogen narcosis slows their breathing down somewhat, or that they are more focussed while deep diving, so dont let their breathing get away on them.