Buddies kept grabbing/pulling me to ascend faster than computer said was safe

[Lorenzoid]

For purposes of a "basic scuba" discussion, it's advisable to ascend at the rate your computer or tables advise you to, not faster or slower. Computers and tables have an ascent rate baked into their logic, and the result you get from using them is only "correct" so long as you obey that ascent rate.

 

[nimoh]

Doesn't that kind of go against decompression theory? The slowest ascent you can make is a stop. And don't people make stops to off-gas?

I get the whole idea of different tissue loads and unloads at different rates. But the ones that are slow to load and unload also won't have as much nitrogen in them.

My understanding is that you can't add a lower partial pressure of nitrogen that has a higher partial pressure. I can go along with the instant you make your ascent you may take on a little more but that should quickly reverse. So my thinking is that you can't ascend too slow unless you only have a couple seconds before your no-deco time is up and you can't get to a shallower depth before you go into deco.

I really want to understand this as it is very interesting to me. So, please don't think I am trolling or starting an argument.

I would recommend reading Deco For Divers by Mark Powell.

Deco for Divers: Decompression Theory and Physiology: Mark Powell: 9781905492077: Amazon.com: Books

 

[azmodan50]

OK, I will leave it alone. We are talking about ascending so slowly as to continue to load nitrogen to a dangerous point. As long as I've been diving and as many classes I've taken, not once have I heard that you can ascend too slow as long as you have enough gas.

Thanks for the responses and I will look into that book nimoh. Thanks.

 

[boulderjohn]

I really want to understand this as it is very interesting to me. So, please don't think I am trolling or starting an argument.

Here are three relatively quick reads for you:

Decompression theory - Wikipedia, the free encyclopedia
http://wrobell.it-zone.org/decotengu/_downloads/mvalues.pdf
Gradient Factors

---------- Post added April 27th, 2015 at 11:38 AM ----------

Doesn't that kind of go against decompression theory? The slowest ascent you can make is a stop. And don't people make stops to off-gas?

Stops to off-gas are made at relatively shallow depths, when almost all tissues are off-gassing. Those stops give those tissues time to off-gas, and they are shallow enough that the gas being breathed has a much lower level of nitrogen.

In contrast, an ascent that is too slow occurs at deeper depths, when most tissues are still on-gassing and when the nitrogen partial pressure in the gas is still relatively high. People don't start an ascent from 90 feet and then do a stop at 85.

 

[Water Boy76]

How slow?

Research supports 30 FPM as a generally accepted safe rate. Most computers use that as the planned ascent rate, as do most decompression software programs. As people have noted earlier in the thread, a fast ascent warning in your computer log is meaningless. It could have happened that you exceeded that rate for a few seconds during an otherwise very slow ascent. Yes, there is such a thing as too slow.

Agreed that's what I was talking about - The fast ascent rate warning (beep and flash) that my computer gives me. Usually for exceeding the rate for a few seconds during a normally slow ascent. When I review my dive log afterwards, the ascent rate graph flashes showing that I ascended too quickly for the entire dive. Obviously not the case. If there was to be a medical emergency it would give the Dr. bad information.

 

[FinnMom]

Snatching at someone else like that is not just asine, it's plain stupid. Even if you did have your computer set to maximum conservative settings and your buddy had a train to catch, you should always avoid doing anything to upset or stress someone that is already a bit anxious.

If harrassed again, you may need to consider use of the international signal for "Thank you, but I do not require your assistance at this time"
=> with other fingers balled into a fist, extend middle finger upwards with the back of your hand facing the other person.

 

[Storker]

you may need to consider use of the international signal for "Thank you, but I do not require your assistance at this time"
=> with other fingers balled into a fist, extend middle finger upwards with the back of your hand facing the other person.

This is one of the reasons I switched from three-finger wetgloves to (five-finger) drygloves

 

[rhwestfall]

this is the appropriate time to either (1) present a BFK, (2) action mirroring a quote from Paladin a few years back of "someone would be eating their mask".....

 

[kr2y5]

Just to ground the "slow ascent" discussion in reality... the NDL for 90 feet dive is 25 min., and the dive lasted 17. If the OP were to ascend for an additional 8 minutes (for a total of 11), she would have been ascending at something like, 1.5 inches per second... and she would have run OOG well before reaching the surface. I think it's safe to say that excessive on-gassing due to the ascent being too slow is not an overwhelmingly large factor in this incident...

 

[redacted]

Just to ground the "slow ascent" discussion in reality... the NDL for 90 feet dive is 25 min., and the dive lasted 17. If the OP were to ascend for an additional 8 minutes (for a total of 11), she would have been ascending at something like, 1.5 inches per second... and she would have run OOG well before reaching the surface. I think it's safe to say that excessive on-gassing due to the ascent being too slow is not an overwhelmingly large factor in this incident...

Unnecessary on-gassing is a detriment to subsequent dives.

But I do agree that the harassment was probably inappropriate. I would have probably been waving G-B from above and keeping an eye on the errant diver as best I could if my PU buddy refused to make a normal ascent.