Required Safety Stop a decompression stop?

[Reg Braithwaite]

You may find some answers within this thread from a few months ago. There is a lot of the same debating as is going on here, but near the end of that thread are some references you may find interesting.

I think I recall that thread, thank you. Tthere are some real gems in there, although I had to plonk someone to make the whole thing coherent. I thought Blackwood nailed the literal subject of this thread:

There's no inconsistency [in terminology].

The difference is that said "required" safety stop isn't required to satisfy the decompression model, it's to satisfy the author of the table annotation (and likely the lawyers turning the screws).

(Where by "nailed it," what I actually mean is, "Expressed in a simple and direct manner what I believe based on light reading and couch surfing." My endorsement is pretty-much meaningless.)

 

[Meng_Tze]

A 'safety stop' is a decompression stop. But because it is not a mandatory deco stop, it is called a 'safety stop'. Mandatory decompression stops come into play when a diver goes beyond the No Decompression Limits (NDL) of a given table.

Omitting a safety stop is not likely to result in DCS instances. Omitting mandatory deco stops, will dramatically increase the risk of DCS the further you are over the NDL.

(this does not take in account variances in gases, environment, exertion etc).

 

[divengolf]

A 'safety stop' is a decompression stop. But because it is not a mandatory deco stop, it is called a 'safety stop'. Mandatory decompression stops come into play when a diver goes beyond the No Decompression Limits (NDL) of a given table.

Omitting a safety stop is not likely to result in DCS instances. Omitting mandatory deco stops, will dramatically increase the risk of DCS the further you are over the NDL.

(this does not take in account variances in gases, environment, exertion etc).

Well put. KISS.

 

[AbyssalPlains]

Unless I didn't pay attention in my beginning tech classes, there is no such thing as REQUIRED safety stop. It's called a RECOMMENDED safety stop. Technically speaking, it is a safety cushion, which, according to the dive tables and algorithms used by computers, is not necessary to prevent DCS. However, since all tables and algorithms are based on mostly empirical and only a little experimental experience, anything you do to allow your body to off-gas can't hurt. The safety stop is just that, a recommended safety cushion. If any dive plan called for a REQUIRED safety stop, it's automatically a decompression stop and the dive no longer a recreational one.

At least in my book.

 

[Mr Carcharodon]

Safety stops are done specifically to decompress, and to reduce the risk of decompression illness.

It is tortured logic to say they are not a decompression stop. You could say the they are not required stops. But to say they are not decompression stops is being oblivious to the physics of decompression, and a pedantic argument.

 

[Blackwood]

Unless I didn't pay attention in my beginning tech classes, there is no such thing as REQUIRED safety stop. It's called a RECOMMENDED safety stop.

Again I must suggest it depends on who/what you are asking.

If you are 'asking' a no-stop decompression algorithm, there is no such thing (as a required safety stop).

But if you are asking people who write instructions for use of certain no-stop decompression tables, there is such a thing.

For example, per PADI's RDP instructions: "A safety stop for 3 minutes at 15ft is required any time the diver comes up to or within 3 pressure groups of a no decompression limit and for any dive to a depth of 100ft or greater."

 

[Blackwood]

• Some tech divers were talking about deco the other day and they said that older deco protocols had them decompressing at the surface, while newer deco protocols have them decompressing in the water. What does this mean, and does it have any relevance for recreational diving?

If they have surface interval requirements (or consider SIT for planning repet profiles), they most certainly do decompress on the surface.

(It's impossible to completely reach equilibrium with 1ATM without actually being at 1ATM. In other words, if there is water above you, there's some decompression left to do.)

What they mean is that modern algorithms - specifically bubble models - attempt to address a subset of the decompression obligation earlier than pure dissolved models do.

And yes, I'd say it has relevance for recreational diving. NAUI, GUE, UTD and maybe some others agree that driving the gradient as high as theoretically safe (i.e. to an M-value) isn't necessarily the best ascent strategy.

 

[don Francisco]

Unless I didn't pay attention in my beginning tech classes, there is no such thing as REQUIRED safety stop.

If you were PADI trained, you might have been napping. While safety stops are always recommended, a 3min.@15' safety stop is required on all dives to 100' or deeper, and/or whenever the diver comes within 3 pressure groups of the NDL.

It still isn't a deco stop if you stay within the NDL, but it becomes a factor when planning multiple dives if the tables you're using assume you're making it.

While no-deco diving is defined as that which doesn't require a deco stop before ascending to the surface, it doesn't mean that there aren't any decompression considerations, ie. allowing 12-24 hours for off gassing before flying.

 

[Reg Braithwaite]

weird SB posting bug, please ignore this post

 

[Blackwood]

^^ you sure about that?