Does cold water increase air consumption?

[carljess]

My wife and just returned from a trip that involved a couple of dives off Catalina island -- that was awesome. But we both went through air at a much faster rate than we have come to expect.

At the first of the year we made 4 dives at Homestead crater outside of SLC. This is very easy diving, almost like a large very warm (92 F) swimming pool. Under those conditions our air SAC was in the 0.6 - 0.7 CFM range. I know -- not great but we are relatively new divers and that is improving, or was improving.

At Catalina, at about the same average depths, we went through air much faster. Calculating SAC's for those dives gives something like 1.1 - 1.2 CFM.

The obvious difference in the dives is the water temperatures, 56 F at Catalina vs 92 F at Homestead. So the question is: Does cold water really increase SAC that greatly? We both were wearing 7 mm wet suits and were chilled by the end of the dives (particularly the second dive) but certainly not hypothermia.

I know that I was very jazzed up about the opportunity to dive at Catalina, and that probably was some part of the increase. But once we were started I thought that we were at ease so I don't think excitement at the chance to dive a great location is the entire answer. There was no real current or surge, the seas were calm.

I do not believe we were overweighted, or at least not enough to affect air consumption. I did a buoyancy check at the end of the first dive and believe weighting was fairly close. With an near empty tank and the BC completely vented I needed slightly more than a normal full breath to float at eye level.

So is this increase something we should have expected because of the temperature? Or alternatively what else should I look into for the increase? Thanks. Any insight is certainly appreciated.

Carl

 

[rmannix]

Yes, even more so if not adequately dressed for it

 

[do it easy]

Yes it does, but there might be other factors at play- you were probably wearing more neoprene than you were accustomed to and also seeing new sights, which can increase the excitement level. There might have been surge or current that might not be present in the Homestead crater.

The short answer is yes.

 

[ecudiver]

absoulutely i did some diving in a local quarry and my computer registered it at 42 degrees and i def. consumed more air than i do when diving in 70 or 80 degree water.

 

[kf6alc]

I think the extra neoprene can restrict movement a bit, and that can increase consumption, but probably the extra weight required affects your rate even more. I know I go thru air faster here in Monterey than in warm water locales. I seem to remember reading somewhere to factor cold water as though you were 10-20' deeper (maybe wrong on that #, but something like that) when planning a dive.

So don't worry, it's not just you!

 

[tstormdiver]

Oh yes it does, can you say "Hoover"? At 80 w/ a AL 63 cuft tank in a quarry at 42 degrees, I'm lucky if my tank lasts more than 20 min.

 

[piikki]

I wonder if it is a given that it does. Generally I believe the fact that it does.

I have lived most of my life in climate very cold. I find that initially when I jump into cold water, whether I am wearing adequate exposure protection or not, I huff and puff more. However after awhile I seem to adjust and breathe slower than usual. Of course if I move frantically to warm up I will use more air but generally my air consumption is little lower on extreme cold dives. Everything slows down a bit.

Comparing to my buddy (who is not from above Arctic Circle like I am), I use less air on <45F dives. This is significant in the sense that during the last year her SAC has been way better than mine by a good margin (we started the same, hers has improved lot more). By subjective report, I have felt colder during these dives, so it's not like she considers she suffered more from the cold than I did. We use same exposure protection.

 

[Sjassi]

Yeah it does. The cold "shock" you get when you enter the water increases your breathing and there for your air comsumption, and the increased physical activity needed to keep warm does the same.

 

[ClayJar]

If everything but the temperature was the same, your body would burn more oxygen just keeping your internal temperature stable, and when you use more oxygen, you breathe more. Of course, there are many other factors (like blood flow to the extremities, the constricting nature of thick neoprene, etc, etc), but it's quite normal to burn air much faster in cold water.

On the other hand, if you're diving in a usually murky site that is completely abandoned in the winter and almost tropically clear, and you're in no hurry to go anywhere, and you are well insulated, it's not a given that you'll go through your air faster. (One of my low SAC dives was also one of my first in a drysuit, even.)

Still, it's customary to burn air faster... perhaps due in part to your body's subconsious knowledge that if it burns air faster, it can go back to the warm, happy place sooner.

 

[Rick Murchison]

I would answer this question this way...
Cold water certainly can increase your air consumption. On the other hand, it doesn't necessarily do that. Some of my lowest SCR dives are in the 45 - 50 F range, when I'm adequately dressed and just cruising along at very low speed - because it's low vis - at constant depth.
On the other hand, I've jumped in when it was unexpectedly colder than I'd figured it would be (two or three years ago we had some unexpected cold water upwelling well into July in the Gulf) and found myself huffin' & puffin' like a steam locomotive
Rick