As evidenced by the discussion in the thread, rightly or wrongly, people often use RMV and SAC in different ways. It is a noble but probably hopeless goal to get everyone on the same page, definitionally. Just be clear to specify your units. Cf/min or L/min at 1ATA is most useful, but if you insist on making me do the math and want to say psi/min, then make sure to tell me your cylinder volume. That's probably the best we can hope for....
OP's specific question was why his gas consumption was lower at depth than on his safety stop. That is backwards from what one would usually expect. My gas consumption on deco is typically a third or more less than during the "working portion" of the dive -- assuming "working portion" is only light/moderate stuff. YMMV.
As to why your consumption is higher on the safety stop than at depth, I can only speculate, but two things come to mind:
First, perhaps your shallow time involved harder work - catching up to the DM, swimming for the boat, fighting buoyancy issues, etc., while your bottom time was a nice drift. Obviously, buoyancy is easier at depth, so if for some reason you were "fighting it" shallow, that could be an issue.
Second, some folks are more conscious about their breathing at depth, aware that they are burning through gas at a much higher rate. Early in the dive, they worry about being the guy who runs low and has to cut the dive short. In response to these things, they try to "conserve," sometimes unconsciously, and that leads to bad habits, like skip breathing. Once they get shallow, they are less worried and breath they way they should have all along.
Obviously, skip breathing is not a good practice, but it might explain "better" gas consumption at depth -- but it isn't really "better." If you have headaches or other indicia of CO2 retention after diving, that would be another indicator of bad breathing habits at depth.
OP's specific question was why his gas consumption was lower at depth than on his safety stop. That is backwards from what one would usually expect. My gas consumption on deco is typically a third or more less than during the "working portion" of the dive -- assuming "working portion" is only light/moderate stuff. YMMV.
As to why your consumption is higher on the safety stop than at depth, I can only speculate, but two things come to mind:
First, perhaps your shallow time involved harder work - catching up to the DM, swimming for the boat, fighting buoyancy issues, etc., while your bottom time was a nice drift. Obviously, buoyancy is easier at depth, so if for some reason you were "fighting it" shallow, that could be an issue.
Second, some folks are more conscious about their breathing at depth, aware that they are burning through gas at a much higher rate. Early in the dive, they worry about being the guy who runs low and has to cut the dive short. In response to these things, they try to "conserve," sometimes unconsciously, and that leads to bad habits, like skip breathing. Once they get shallow, they are less worried and breath they way they should have all along.
Obviously, skip breathing is not a good practice, but it might explain "better" gas consumption at depth -- but it isn't really "better." If you have headaches or other indicia of CO2 retention after diving, that would be another indicator of bad breathing habits at depth.
