Since this is the basic forum - I really feel some misconceptions need cleared up.
My point was (and remains) that for recreational NDL diving, in the rare case you encountered a deco obligation that required a stop, a 85/85 GF setting is unwise.
I'd much rather take that first stop at 6m, rather than at 3m
Safety stops are considered somewhere between 3 and 6m - in PADI we teach 5m. 10' stops are quicker but harder for newbies to hold, 20' stops are easier to hold and keeps you safer from boat traffic, 15' stops are right there in the middle. The key is get above 30' but we don't really teach that key in recreational diving, you learn it later in Deco classes.
The difference in safety stop depths is difference in pressure gradients - the higher the pressure gradient, the faster the off gassing. Faster off gassing must be controlled, that is why decompression divers stop at say 40, 30, 20 and finally 10' during their decompression. For recreational diving, it is suggested by PADI and SSI that your safety stop depth be 15' which is a fantastic safe simple depth.
I posted profiles from two dives that could easily be a "mistake" made by someone - actually big mistakes. Both profiles show the first and only stop required being the 20' stop - my computer is set for the safety stop to be at 20'. For my open ocean, heavy boat traffic diving - 20' is the safer choice for my stops.
The difference between 45/85 and 85/85 is virtually nill when following recreational diving safety stop depths of 15' - fact is follow your computer.
If you end up getting 5 minutes of deco, the computer will bring you up safely (and probably more conservative than 85/85).
If you've violated NDL and gone into deco - the computer will direct you just as it's set - not any more liberal or conservative. The computer is a math processor and doesn't care if you are in deco or just fine - it does NOT get more conservative once you have entered deco.
Computers - if you have one, understand it - it's a powerful tool to assist you in diving safer. Most rec computers I see have different levels of conservatism - understand what the levels are. IMO, computers that relate to GF numbers are much easier to know where you are at verses micro bubble numbers like Suba Pro uses. GF numbers require some learning and understanding of what they are, how they effect the dive and where your body is at theoretically - especially if you alter them from basic settings.
@wstorms,
@Fastmarc,
@ChuckP, and
@rjack321 again this for an unplanned deco obligation (rec diving does not involve deco)
If I had the Mares running 85/85 and had an unplanned deco obligation, I certainly wouldn't do my first stop at 3m.
My primitive understanding of the Buhlmann algorithm is that the GFlo setting won't materially change the amount of deco time. What it will change is where your stops are and how long you need to spend at each stop
Again, recommended safety stop depths for recreational diving are 15-20' - and staying within those depths will have a nill effect on 40/85 verses 85/85.
GF low determines the depth of your first stop. GF low of 40 means that you will stop when the leading tissue compartment is at 40% of the M value.
GF low can and does have an effect on total run time of the deco.
Deco stop depths and time are determined by the line between GF lo and hi - the GF high number is where you are at in relation to the M value when deco is complete.
You may notice on my dive profiles, I did not surface once deco was complete - I stayed at 20' for a few minutes longer. Shearwater computers allow you to monitor your SGF number and as an added margin of safety, most times I stay down till SGF is at 75 or below - no hurries.
It's 'more sporty' than I would prefer. No one understands what causes a person to take a DCS hit, all anyone can do is mitigate the risk. In my experience, you would have to incur a pretty large deco obligation to not have it clear as you ascended so this whole sub-thread could be us considering how many angels could dance on the head of a pin.
Remember, this sub-discussion started with @FeedFlyFreak saying 85/85 was his preferred setting for warm water NDL dives.
In my experience that is far from the truth UNLESS you get above 40 if not 30' and spend time. I have tried many times to see what it would take to clear 3-4 minutes of deco, it just doesn't go away untill you get up above 40' and really not till you hit 30'. We have many dives where the middle portion is in the 60' range and it don't go away, 50' don't go away, 40' ehh not really - you really have to get above 30' to have your fast compartments off gassing.
Remember, these are NDL dives - GF high is the number you worry about and whatever that number is depends on the individual diver. I can tell you a GF high of 80 is very close to a Scuba Pro MB=1 settiing. I can also say I see a lot of people diving Shearwaters set at medium.
Also, the GF high number is how rec divers relate to NDL, there was a poll somewhere on this board asking what the average GF people exited the water was and I think it was 60 or below.
NDL recreational diving is fun, it can be safe but requires you all the divers to look out for yourselves. There is no reason to "fall into deco" - stay five minutes away from deco at least. Ascend slowly, casually - do a five minute safety stop at 15 foot and ascend slowly to the surface. There's no hurry, no rush.
