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There is certainly enough information concerning sub clinical DSC to substantiate a change in my attitude toward ascents. (read as blow and goes for the fun of it).
Ive been reading a bunch of stuff on the RGBM model and all the stuff on the DAN site. Old dogs can learn new tricks. Thanks!
 
dugout:
When did the "Safety Stop" come into vogue and why? ... What's the point of the safety stop?

I missed this question first time through your thread, anyway Not really sure when they came into vogue, they've always been a part of my diving, but the purpose is to allow the deep tissue gas to escape more efficently. Rember Boyels law (I think) the most dramatic expantion of gas occurs in the first atmospher of depth between 1-30 ft by hanging out at 15 ft for a few minutes we allow a dramatic amount of off gassing to occur that normaly would take a longer period of time to happen on the surface so in therory it shortens your surface interval and lowers your presure group.

Something thats new that they just started to encourage is stop at half your max depth, and then another at 15ft. Seems like sound logic but to me just seems like the safety bug gone mad.
 
Tagerisatroll:
Rember Boyels law (I think) the most dramatic expantion of gas occurs in the first atmospher of depth between 1-30 ft by hanging out at 15 ft for a few minutes we allow a dramatic amount of off gassing to occur that normaly would take a longer period of time to happen on the surface
QUOTE]

Not quite right. The rate of off gassing is determined by the differential pressure so you would off gas faster on the surface but the higher differential could also possibly cause bubble formation if blood gas tension is high enough. THe stop allows off gassing to occure over a longer time and at a slower rate and differential pressure to hopefully prevent bubble formation of a size that can cause symptoms of DCS
 
Something thats new that they just started to encourage is stop at half your max depth, and then another at 15ft. Seems like sound logic but to me just seems like the safety bug gone mad.


After discussing this with some of my fellow divers I have been doing it. I'm not exactly a young cat anymore and it does seem to cut back on some of the post dive(minor) headaches I've experienced from time to time. I've done this on all my dives this season that were inexcess of 90 fow that were within the NDL's. For my deco diving I have been using V-planner set for +2 and that seems to work well too.
When I started out, everyone used the Navy tables and that was fine as I was 18. Now that I'm on the long side of my forties I feel I have have to be a bit more careful.

Jim
 
Tagger.. mentioned shortening you surface interval if you do multiple safety stops. If you follow the 40 ft 1 min, 30 ft 1 min, 20 ft 1 min, and 15 ft 3 min, how do you calculate your new necessary surface interval. The tables I use don't factor safety stops. Since the computers are really just based on the same algorithims that the tables are can they calculate it correctly? Thanks.
 
coldsmoke:
Tagger.. mentioned shortening you surface interval if you do multiple safety stops. If you follow the 40 ft 1 min, 30 ft 1 min, 20 ft 1 min, and 15 ft 3 min, how do you calculate your new necessary surface interval. The tables I use don't factor safety stops. Since the computers are really just based on the same algorithims that the tables are can they calculate it correctly? Thanks.

My computer only credits a safety stop at 20-15ft range so the simple answer to your question is no most computers won't, also most tables won't either, I believe the Naui tables have built in 3 minute safty stop at 15ft that shortens the surface intervals. The newer guideline of the stops at half you max depth is a relitivly new and as I understand it doesn't really effect the tables just your actual physilogical nitrogen load, and is Just for safety not actually increasing your diveable times or decreasing surface intervals. But as far as the tables are concerned as it was explained to me they credit the time just like the had been done at 15ft. (I'm not sure on this as I wasn't really paying attion to the particulars because I never planned to do it I do all my safety stops at 18-15ft. where my dive computer will credit the time)

But as some of the divers have posted in this thread they have felt better after the dive having followed the newer protical. I not really hot on the idea of safty stops at deeper depths because I'm kind of an air hog anyway, and unless i've gone deco I want to get back up to a lower air consumpution range as soon as possible once I've left the bottom. And since my computer is not going to start counting the stop until 20ft whats the point. I haven't ever suffered from some of the post dive headaches some of the other divers have described. But I know alot of divers that swear by it and it defentily won't hurt to stay in the water an extra couple minutes if you got the air.
 
Hey Dugout,
Alive and well in o.c. Maryland. We do a lot of diving 3/4 of the year and spend alot of time hashing out methods to do it better. I got my naui card in 81, got out of diving, then back in. A lot has changed, and for the better. Drop me a line if you want to go diving, or talk to Matt at Pirate scuba on route 50 west o.c.
Eric
 
coldsmoke:
The tables I use don't factor safety stops. Since the computers are really just based on the same algorithims that the tables are can they calculate it correctly? Thanks.

I'm confused about this question. Could you explain more what you mean? Sorry if I am being dense. I don't know a ton about the various algorithms used by various manufacturers, but it seems to me that the significant difference is that if the computer is calculating in increments that are much closer to real time, it is going to give a picture that is more reflective of the likely state of your tissues. This is very different from what a table tells you, which is simply an estimate of what you thought you were going to do before you went.
The net result may be that computers let you dive closer to the limits, and therefore reduce saftey margins, but they also deal with variance from the planned depth and times and "multilevel" dives.
Also could tell me what you mean when you say the computer doesn't credit you with the safety stop? Which computer, why?
Thanks
 
Chasanova,

I could be wrong - I am certainly no expert on dive computers but I think that they are similar to the dive tables in which they only calculate gas loading and don't give credit for stops. They do calculate constantly and consider different depth changes but I believe at stop depths they are just calculating that you are absorbing less gas or no gas rather than giving you credit for gas dissipation from your soft tissues. On that note, I remember being told one time that you don't actually dissapate any nitrogen at the 15 foot depth anyway - don't remember where I got that info and it could be wrong, but I think it's safe to say that any gassing off you may do at the safety stops is likely to be insignificant. In no-deco diving I believe it's just personal preferance - everybody has different physilogy - I personally have never experienced the headaches that others are talking about. So I only do the shallow safety stop and that is mostly just because I like it in the water. I just posted the question out of curiosity.
 

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