Scared I Missed Safety Stop

[boulderjohn]

I too do not understand why I was taught that the safety stop was mandatory on dives deeper than 30m.

It is still the official statement when using the PADI RDP.

Before the PADI RDP, people used the Navy tables, and they were really not the best for recreational dives because they called for extremely long surface intervals. Most Navy divers only did one dive a day, so it didn't matter to them, but for recreational divers trying to do a two tank dive with AL 80s, it was a problem. PADI did extensive research on the kind of diving done by recreational divers and found that for people doing such dives within certain parameters, it was quite safe to use a system that led to shorter certain intervals, and they created the PADI RDP to guide such dives. Their goal was to create a simple dive table that could be used by that kind of diver under those circumstances.

The more complicated Navy tables went beyond those recreational limits and introduced decompression stops at certain depths and times. The need for such stops increases gradually with increasing depth and time. PADI wanted to produce a table for dives that did not require those decompression stops, and that is what they did. They did include the idea of a safety stop to be, well, safe. These were physically the same as decompression stops, but they were taken at depths and times that did not normally require decompression stops in the Navy tables, so they gave them a different name and said they were just recommendations.

There were times, though, that divers were really close to the depths and times when decompression stops were going to be required. With the goal once again of being safe, PADI decided to make the stops mandatory then. These really were decompression stops, but I suspect (don't know for sure) that they decided to stick with the safety stop language for simplicity, saying that they are recommended in some cases and required in others. Dives to 30 meters (100 feet) are among the reasons for a safety stop to be mandatory. It is really a decompression stop, but that is just language.

 

[Freewillow]

There were times, though, that divers were really close to the depths and times when decompression stops were going to be required. With the goal once again of being safe, PADI decided to make the stops mandatory then. These really were decompression stops, but I suspect (don't know for sure) that they decided to stick with the safety stop language for simplicity, saying that they are recommended in some cases and required in others. Dives to 30 meters (100 feet) are among the reasons for a safety stop to be mandatory. It is really a decompression stop, but that is just language.

Thank you bolderjohn for this description. Maybe two remarks:

1. All stops at a shallow level are DECO stops, in the sense that they help eliminate nitrogen from your tissues. As I said that you call them "Safety" stops or "Deco" stops is a question of language. Safety stops, made mandatory by PADI is an extra safety over and above tables.

2. My second remark is that I havec not seen many divers that still use PADI Dive tables in the real world. In a lot of parts of the world, divers have to have a dive computor. These dive computors, as you know, are not following US NAvy tables anymore. I will not, this is a basic scuba forum, go into the different algorythms that are used to calculate NDL ( no deco limits ) real deco procedures etc..... Most of them are much more careful than navy tables but that does not mean that everydive will be DCS free. The fact that you add "safety" stops just decreases the change of DCS but nothing more.

A final remark for another member, about the 30m/100 feet limit were safety stop would be required. Nice to keep a number in mind but everydiver should know that saturation levels are a function of PPN2 ( partial pressure of Nitrogen) X time. So I would rather take a safety stop at 25 m (75 feet) for 30 minutes as opposed to 35m ( 110 feet ) for 10 minutes

 

[boulderjohn]

Thank you bolderjohn for this description. Maybe two remarks:

1. All stops at a shallow level are DECO stops, in the sense that they help eliminate nitrogen from your tissues. As I said that you call them "Safety" stops or "Deco" stops is a question of language. Safety stops, made mandatory by PADI is an extra safety over and above tables.

2. My second remark is that I havec not seen many divers that still use PADI Dive tables in the real world. In a lot of parts of the world, divers have to have a dive computor. These dive computors, as you know, are not following US NAvy tables anymore. I will not, this is a basic scuba forum, go into the different algorythms that are used to calculate NDL ( no deco limits ) real deco procedures etc..... Most of them are much more careful than navy tables but that does not mean that everydive will be DCS free. The fact that you add "safety" stops just decreases the change of DCS but nothing more.

A final remark for another member, about the 30m/100 feet limit were safety stop would be required. Nice to keep a number in mind but everydiver should know that saturation levels are a function of PPN2 ( partial pressure of Nitrogen) X time. So I would rather take a safety stop at 25 m (75 feet) for 30 minutes as opposed to 35m ( 110 feet ) for 10 minutes

Thanks...more follow up.

On my first diving after being certified back in the last millenium, I attempted to use my PADI tables for a dive in Cozumel. Everyone laughed at me. That remains the only time I ever saw anyone attempt to use those tables outside of a training session.

In its current courses that use computers, PADI says to follow your computer algorithm for ascent rates and ascent profiles. It also recommends that you do a safety stop on most dives.

PADI has also stopped using the phrase "No decompression diving" or No decompression limits" because of the fact, as you note, that all diving requires decompression. They correct phrase now is "No stop diving" for dives in which a safety stop is not required.

 

[Freewillow]

Make sense boulderjohn. Happy diving

 

[Basking Ridge Diver]

I dont have an issue with using computers - I own one and so does my son.
My concern is that my son will rely only on the computer and not use his brain to reaffirm his computer readings. There is a very strong benefit in my opinion in using and understanding how the tables work and I also believe the same for repetitive dives. If you use the tables enough you begin to see and remember the "magic" numbers - those being used for No Stop diving as well as residual nitrogen. The RAT formula should be understood and reinforced in my opinion through tables so that you understand how it works and what it is doing in relation to your next dive.
Computers in my opinion don't give you the knowledge behind the numbers - it only spits out numbers and it is up to you to ensure you understand what it means. Using the tables makes you ask questions so you begin to understand what it means...
I am not suggesting we go back to old school slide rules - only that we understand the reasons behind the tables so that we can understand the computer and what it is telling or not telling us.

 

[100days-a-year]

Yeah,they fly multi million and even billion dollar planes armed with thermonuclear weapons with computers,expensive and redundant but still just computers.

Understanding is a relative term in any case as the variables quickly get out of the ability of anyone to process even with a computer.

I do agree there are far to many incompetent divers that are tragedies waiting to happen but even with a math background,thousands of dives and years of experience my best guess is still a guess and tables are just a part of understanding dive physiology.

Our best and brightest come up with algorithms that are "mostly safe" at best.

 

[Freewillow]

with basking ridge diver on that one :cheerleader:

 

[RedyTedy]

Hey everyone, I looked over this thread and was astonished by 4 pages of replies. Your posts were all very interesting!

I obviously didn't get DCS, and I know that I ascended nowhere near 80 ft per second.

I dive very infrequently and have a dive trip coming up this summer. Would a dive computer be a worthy investment, or would it be okay to study dive charts and bring my PADI dive calculator? I will be diving consistently with a group for a week so I'm leaning towards no dive computer.



Side note: would this be considered "necro posting"? The thread wasn't active for a week and I wouldn't want anyone getting mad at me.

 

[Agility]

You need some sort of timing and depth measurement even if you dive tables, so why not take a computer that does both and keeps track of your nitrogen load for you. Getting a cheap (or second hand) divecomputer is a good idea IMHO as long as you understand what it is trying to tell you.

 

[TSandM]

Almost no one uses tables. If you are diving with a group, the group won't enjoy the short bottom times you will get from tables.