Diveral
Contributor
Dove the Navy Dive Tables for 25 years until I started using computers last year. They show a 15 min NDL at 120' 10 min at 130 & 140 and 5 min from 150-190 feet. Note most of that is beyond today's recreational limits.
Limits? Safety stops? Conflicting info- help?
- Thread starter susan6868
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lamont
Contributor
If you are worried about running out of air at depth and needing to "pop" to the surface immediately, you should probably stick to 60 feet as a max depth. I believe that even the PADI RDP suggests that for depths below 100 feet that you must do a mandatory safety stop?
For beginning divers you should stay above 60 feet. The "air clock" (how much you have left) and the "deco clock" (how much NDL you have left) run relatively slowly there. There are no scuba police, but you can get into quite a bit of trouble at 100 feet, particularly if you're only carrying an Al80. At 130 feet you get into trouble almost immediately if you don't have the training or experience.
For a typical newbie SAC rate of 0.75 cu ft / min on an Al80 you are using about:
surface - 300 psi / 10 min
33 feet - 600 psi / 10 min
66 feet - 900 psi / 10 min
100 feet - 1200 psi / 10 min
130 feet - 1500 psi / 10 min
And the time a tank will last you before you suck it dry goes like:
surface - 100 mins
33 feet - 50 mins
66 feet - 33 mins
100 feet - 25 mins
133 feet - 20 mins
If you reserve enough air to get you and a buddy back to the surface safely and do your stops, you need more gas as you get deeper:
33 feet - 700 psi
66 feet - 1000 psi
100 feet - 1300 psi
130 feet - 1800 psi
Now at depth you run over your reserve limit in a shorter and shorter time:
33 feet - 38 mins
66 feet - 22 mins
100 feet - 14 mins
130 feet - 8 mins
Mess up at 130 feet and the margin for error is much smaller -- in 8 minutes you've hit your reserve limit and your NDL -- 12 minutes later its all over.
For beginning divers you should stay above 60 feet. The "air clock" (how much you have left) and the "deco clock" (how much NDL you have left) run relatively slowly there. There are no scuba police, but you can get into quite a bit of trouble at 100 feet, particularly if you're only carrying an Al80. At 130 feet you get into trouble almost immediately if you don't have the training or experience.
For a typical newbie SAC rate of 0.75 cu ft / min on an Al80 you are using about:
surface - 300 psi / 10 min
33 feet - 600 psi / 10 min
66 feet - 900 psi / 10 min
100 feet - 1200 psi / 10 min
130 feet - 1500 psi / 10 min
And the time a tank will last you before you suck it dry goes like:
surface - 100 mins
33 feet - 50 mins
66 feet - 33 mins
100 feet - 25 mins
133 feet - 20 mins
If you reserve enough air to get you and a buddy back to the surface safely and do your stops, you need more gas as you get deeper:
33 feet - 700 psi
66 feet - 1000 psi
100 feet - 1300 psi
130 feet - 1800 psi
Now at depth you run over your reserve limit in a shorter and shorter time:
33 feet - 38 mins
66 feet - 22 mins
100 feet - 14 mins
130 feet - 8 mins
Mess up at 130 feet and the margin for error is much smaller -- in 8 minutes you've hit your reserve limit and your NDL -- 12 minutes later its all over.
tracker
Guest
Web Monkey:
Very good points here. Short history. Learned in 1981. Third dive after class in Subic Bay, beach dive, 140' 'cause buddy left me. Had 1500 left in tank. Ran out of air at around 40', because I was at 140' with 1500 left. Re-cer this year. I'm not an expert, but, I think I unerstand that I can go down faster than I can come up. Back then we were taught differently, front mount/back plate, go down, come up. I have learned a lot from my classes and everyone on this board, but I stick to a rule, if I feel I pushed my depth limit(personally), then hang out at 15' for a couple of minutes. It's all about having fun, and there's nothing wrong with added safety.
ianr33
Contributor
I love that phrase "mandatory safety stop"
Can anyone explain the difference between a mandatory safety stop and a deco stop ??
Can anyone explain the difference between a mandatory safety stop and a deco stop ??
H2Andy
Contributor
yes...
deco stop is spelled "d-e-c-o s-t-o-p"
and mandatory safety stop is spelled "m-a-n-d-a-t-o-r-y s-a-f-e-t-y s-t-o-p"
deco stop is spelled "d-e-c-o s-t-o-p"
and mandatory safety stop is spelled "m-a-n-d-a-t-o-r-y s-a-f-e-t-y s-t-o-p"
H2Andy:yes...
deco stop is spelled "d-e-c-o s-t-o-p"
and mandatory safety stop is spelled "m-a-n-d-a-t-o-r-y s-a-f-e-t-y s-t-o-p"
If folks look closely at the shaded area rules on the PADI tables, there is an interesting point there regarding that safety stop.
From the original post..... remember to keep very conservative ascent rates. Popping to the top doesn't help anyone.....
Sting J
Registered
Susan it is was not a bad question at all. I am glad to see that no one flamed you. The terminology, different agency recomendations, certification levels, and age groups can be overwhelming. Recommendations change over time as well. Especially, to try to absorb it all in a short period of time.
PADI Recreational Depth limits are found on page 204 of the Open Water manual.
60 ft Novice
100 ft recommended
130 ft absolute
What that means is 130 ft is the hard limits. 100 ft is the soft limits for suitably trained divers. For example deep specialty divers or Adv. Open Water with training in similar depths and conditions. 6o ft is the limit for new Open Water divers.
Yes, there are different limits for Junior divers. Ages 10-11 should stay above 40 ft. Ages 12-14 60 ft same as adults, and should stay above 70 ft even after adv. open water class. Though as a parent you may enforce stricter depth restrictions if you see it necessary of course. I have taught and dove with many children they are often near fearless in the water. Fearlessness, is often the only issue.
Required or not safety stops are good buoyancy control practice on every dive. If you make a habit of only doing them on the deeper dives... you may forget to do them when you are supposed to. I have been guilty of that more times than I would like. Of course that was in the days before dive computers had saftey stop counter modes. The required safety stops lets say are highly highly highly recommended. But please do not panic if you have missed one. Panic may be more dangerous in the water then the chance of DCS.
Also Padi recommends a max ascent rate of 60 ft per min while SSI tables recommend a max of 30 ft per min if I remember correctly. That is just trivia. Though the agencies do not agree on all the figures, they do agree that conservative is always good.
Happy Diving!
Jon
PADI Instr #192385
P.S.
Susan I am unclear from your posting if your family are all PADI certified or not. If not you may be arguing over different recommendations... from different agencies... from different eras in training...or different tables...there is nothing wrong with leaning toward more conservative recommendations like you say you do, in fact that is a good thing usually.
PADI Recreational Depth limits are found on page 204 of the Open Water manual.
60 ft Novice
100 ft recommended
130 ft absolute
What that means is 130 ft is the hard limits. 100 ft is the soft limits for suitably trained divers. For example deep specialty divers or Adv. Open Water with training in similar depths and conditions. 6o ft is the limit for new Open Water divers.
Yes, there are different limits for Junior divers. Ages 10-11 should stay above 40 ft. Ages 12-14 60 ft same as adults, and should stay above 70 ft even after adv. open water class. Though as a parent you may enforce stricter depth restrictions if you see it necessary of course. I have taught and dove with many children they are often near fearless in the water. Fearlessness, is often the only issue.
Required or not safety stops are good buoyancy control practice on every dive. If you make a habit of only doing them on the deeper dives... you may forget to do them when you are supposed to. I have been guilty of that more times than I would like. Of course that was in the days before dive computers had saftey stop counter modes. The required safety stops lets say are highly highly highly recommended. But please do not panic if you have missed one. Panic may be more dangerous in the water then the chance of DCS.
Also Padi recommends a max ascent rate of 60 ft per min while SSI tables recommend a max of 30 ft per min if I remember correctly. That is just trivia. Though the agencies do not agree on all the figures, they do agree that conservative is always good.
Happy Diving!
Jon
PADI Instr #192385
P.S.
Susan I am unclear from your posting if your family are all PADI certified or not. If not you may be arguing over different recommendations... from different agencies... from different eras in training...or different tables...there is nothing wrong with leaning toward more conservative recommendations like you say you do, in fact that is a good thing usually.
Sting J:
These are the limits I remember from my PADI course. The 60 feet was not emphasized, but the 100ft was emphasized as the limit. ie plan dives to no deeper than 100ft, that way if you accidentally go too deep it is to 110 or 120 or 130 instead of 140 or 150 or 160.
H2Andy
Contributor
Sting J:
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read the Terms of Service and you'll see that the Staff and members
strive to keep ScubaBoard friendly and attack-free.
Amphibic
Contributor
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