Is my air consumption...bad-ish?

[Altamira]

Stop fretting about your SAC/RMV rate and enjoy your diving. Your SAC/RMV is what it is now, and will likely continue to improve with increased dive proficiency and experience. Also, when comparing who came up first or last, you probably don't know who started with a 3250 psi fill vs a 2840 psi fill (AL80s). I have had both readings, and everything in between on dives, and I just dive with the tank I get, fulling realizing that if I get the 2840 psi tank, I am not going to be able to stay down as long as if I had more air. Somebody is going to come up first. Sometimes it will be you, and other times, it will be another diver.

 

[Esprise Me]

Are you diving the same tanks as others? In NC many divers dive HP100s, myself included, and I have dove with divers diving 120s. If you are diving AL-80s (which are not even 80) you will have less air.

This. I was on a night dive once with a group that included a tall guy who couldn't stay off the bottom. As we turned the dive and started heading back toward shore, I was getting cold but figured that guy would surely have to thumb the dive soon based on his air consumption. I was averaging around .6 and had a steel hp-100; someone else was always calling the dive for me. I waited, and waited, as we meandered back, the photographer in the group stopping for several minutes at a time to take pictures. Finally, we got to the shallows where the surge forced us to surface. My air was getting low by then; I would've had to ascend soon anyway. Tall guy boasted that he still had 1,000 psi. I couldn't believe it. I spent the walk back to the car trying to ballpark the numbers in my head--how good did one have to be on air to do that dive and come back with that much? After I'd spent 20 minutes torturing myself I overheard that he was diving a steel HP-120. I had never seen one and didn't realize how much they look like 100s.

Another possibility to consider is that those divers that come up 10 minutes after you are spending longer at their safety stop and coming up with less reserve. It's good to be back on the boat with at least 500 psi, but in good conditions where you're not likely to face problems between 15 feet and the ladder, some divers find it acceptable to come up with less, especially if it gives you more time to offgas in the shallows after a deep dive. You'll go through air very slowly hanging on the anchor line at that depth, and if there are pretty schooling fish or sharks around, it can be a very pleasant extra few minutes.

Finally, are you sure you're all descending together? I was on a boat with both rec and CCR divers recently. The captain made it very clear we were all to be back on board an hour after they opened the gate. The CCR divers were more than 30 minutes late coming back from the first dive, forcing the captain to change the plan from going to a different site for the second dive to having us do the second dive at the same site, with the CCR divers having to sit that one out. One of the CCR divers got a little belligerent when confronted, insisting they were only down an hour. We had to let them in the water first for the third dive, and they were nearly 45 minutes overdue again. I was the last one in the water for the third dive and saw the CCR divers still at the surface, fiddling with their gear, as my buddies and I descended. Morals of the story: those guys were probably jerks, and not every minute in the water is a minute of dive time or gas used.

 

[BRT]

Yeah, that's what I've always figured - that I'm in the totally solid but not amazing range. I guess my faith in myself was shaken today in Cozumel when I hit reserve pressure first, sent up my SMB and did a safety stop solo, and was back on the boat with 500 PSI where I waited a full 10 minutes for the other 6 divers in my group to surface. I was like, wait, am I the air hog??? Downloaded the dives to Subsurface tonight, and yep, SAC was right at 0.47 cuft/m for that dive.

How much air did the others come up with?

 

[mi000ke]

I am pretty much the same as you in terms of build and SAC rate. On the easiest, slowest dives I'm at about .35 - .4 and for dives that move faster or when fighting a bit of current I'm at .5. Almost all my other dives are just around .45. I boat dive with a lot of the locals (both men and women) here on GC, many of which have way more dives than I do, and I am almost always one of the last to come up (and usually one of the first to go in). Based on my limited sample, I would say .45 is above average and a pretty good SAC especially given your number of dives. There are SAC rate polls online here at SB you can search for to see where you stand, but again as I recall you would be above average. That said, my daughter who has done a total of about 10 dives has a SAC of around .3. Go figure.

 

[wnissen]

I would not use the SAC polls around here because they only poll Scubaboard participants, who are among the most active and enthusiastic divers. For instance, Scubaboard polls show an overwhelming majority of the people here use backplate and wing. What fraction of divers in the real world do you see in that configuration? Maybe 10-20%? It's not fair to compare yourself to people who have 10x the dives.

I'd second the sentiments above that you don't necessarily know other people's air. A steel 100 and an aluminum 77.8 with lots of wear are hard to tell apart as they have the same diameter and only a few cm difference in length. But the former has over 25% more air! And you never know what people are really surfacing with unless you ask. One of my instructors has no problem getting back with less than 35 bar / 500 psi but I'm always aiming to never breach that threshold.

That said, some people use very little air for their size. There's only so much you can do about it. Increase your aerobic fitness. Get real relaxed, almost bored, underwater. Stay a bit high if you think you need to. If you're not turning very early, I wouldn't worry about it.

 

[scubadada]

Hi @anchochile

I would say your RMV is somewhere in the average range. Both polls asked for average RMV. As @wnissen mentioned, there are several caveats in interpreting SB polls. Both you and wnissen are active SB participants

 

[Kmart921]

Yeah, that's what I've always figured - that I'm in the totally solid but not amazing range. I guess my faith in myself was shaken today in Cozumel when I hit reserve pressure first, sent up my SMB and did a safety stop solo, and was back on the boat with 500 PSI where I waited a full 10 minutes for the other 6 divers in my group to surface. I was like, wait, am I the air hog??? Downloaded the dives to Subsurface tonight, and yep, SAC was right at 0.47 cuft/m for that dive.

Anecdotally, I've noticed that some divers play a little bit fast and loose with the 500 PSI rule--particularly in places like Cozumel where the dive ops might not necessarily care as much as operators in the US. If one is willing to hit the surface with 200 PSI instead of 500 PSI, one could theoretically squeeze another 10 minutes or so out of a tank on a shallow dive. I don't necessarily endorse this behavior but I definitely know of a couple divers who sucked their tank dry on the surface while waiting for the boat after a 70 minute dive in Coz.

All this to say that not everyone in your group may not have actually ended up back on the boat with 500 PSI. So don't worry about it.

 

[scubadada]

When you are drift diving and have absolutely free access to the surface, the 500 psi surfacing pressure makes less sense, not that it is a good excuse.

 

[Kmart921]

When you are drift diving and have absolutely free access to the surface, the 500 psi surfacing pressure makes less sense, not that it is a good excuse.

For sure. I would be lying if I said I always surfaced with >500 psi in Coz. But you gotta be comfortable floating on the surface. I saw some people getting stressed out and sucking down their tanks when we had a 15 minute wait for the boat in choppier waters. Especially for a relatively new diver, it helps to keep something in reserve.

 

[scubadada]

For sure. I would be lying if I said I always surfaced with >500 psi in Coz. But you gotta be comfortable floating on the surface. I saw some people getting stressed out and sucking down their tanks when we had a 15 minute wait for the boat in choppier waters. Especially for a relatively new diver, it helps to keep something in reserve.

I generally do not breathe off my cylinder on the surface. I get plenty of practice in bigger seas in SE Florida, especially, this time of year .