When to do a safety stop?

[OnTheMark]

I generally do the ‘jaws’ music in my head when the safety stop is up from 15ft and surface on the ‘du NUH NUUURRHHH!’

I think this would make me swim faster, not slower

 

[scubadada]

Some good points above, @JimBlay @Scuba Lawyer and @boulderjohn stuck out to me

Between 1970 and 1980, I also did a couple hundred dives on Navy tables, with a direct ascent to the surface, at a rate up to 60 ft per minute. Obviously, I survived to tell the tale.

I have routinely done safety stops for dives over 30 feet since I was recertified in 1997. My ascent rate dropped to 30 ft per min. Initially, all my stops were for 3 minutes. Later, I increased my stop time to 5 min if I he come within 3-5 min of NDL. Lastly, I slowed down my final ascent to 15 ft per minute. When doing light deco, I would pad my stop by an additional 3-5 min.

For the last 15 months, I have been diving a Teric. Now, I hold my safety stop or deco stop until my SurfGF has decreased to an acceptable level for me. For less aggressive dives, I do a 3 min safety stop, just because.

 

[TMHeimer]

I'd go with the over 30' idea. But if you do a shore dive down to 50', don't stay at that depth very long, and gradually follow the bottom back up a gradual slope to the shore you are probably even better off than the same dive from a boat with the safety stop at 15'. But, that's just an educated guess.

 

[wnissen]

So, I've seen blanket statements that you should always do a safety stop. However, this can't really be the case. If I'm diving in 10-12' of water, surely I don't descend to 15', wait 3 mins and then ascend.

I feel sure that at 60' I would do a safety stop, but what about less than 33'? And even in-between; would you do a safety stop at 40'?

I want to be safe but also not ridiculous. Thanks for your help

You're absolutely right that the safety stop is not needed from a DCS standpoint unless you spend significant time below 10m.

However, the mindset of a safety stop is extremely helpful no matter what depth you're at when you ascend. It's a great opportunity to get yourself ready for the final ascent, which is the most dangerous point for your typical rec diver. People have given themselves lung overexpansion injures by holding their breath while in water shallow enough to stand in! I use the safety stop to start tracking particles so I can maintain a steady position, make sure my BCD is in fact as empty as it should be, get used to any change caused by my 8mm suit uncompressing, and otherwise take a breather and make sure I'm not rushing. Personally, I get some mild vertigo as my ears fizz on ascent, so hanging out below any chop at the surface gives my stomach a chance to settle.

The other time you shouldn't do one is if you, your buddy, and/or your captain have agreed to skip the stop in the case of separation or recall by the boat.

 

[rob.mwpropane]

I hesitate to write this because so few recreational divers have the right equipment for it, but some computers can give you real insight into the need. Since I have such computers, I will describe how it has changed my personal procedures and what I have learned about safety stops from following those procedures. That learning may be instructive to people without those computers.

The idea of a slow ascent during an NDL dive is to allow tissues to off-gas enough nitrogen to make it safe to go to the surface and the greatly reduced pressure there. The last 10-20 feet of the ascent is when pressure drops dramatically, so the idea of stopping at that level for a few minutes just to be sure was developed, and that is the purpose of the safety stop. Some modern computers will give you a reading of what your surfacing pressure will be relative to that theoretical maximum safe pressure (gradient factor) if you were to surface at that moment. In theory, that will tell you how necessary it will be to do a safety stop, or how long to do it. If the reading (surfGF) is 70, then if you were to surface at that moment, the nitrogen pressure in your tissues would be about 70% of what is considered safe, so that would be considered a pretty safe pressure. If you were to arrive at safety stop depth with a surfGF of 70, you would probably not have much of a need for a safety stop.

So after doing this for a while, I see that if I do not come all that close to the NDL on a mid range dive (say 70-90 feet), I don't really need one. If I do get close to NDL on such a dive, then the typical 3-5 minute stop will get me to a nice, safe range. In general, if I get within a few minutes of NDL on ANY dive, a safety stop does a pretty good job.

Note that I am using how close you get to NDL as a metric rather than depth. That is because I dive mostly with nitrox. (The place in Florida where I get my tanks filled where I do my NDL diving gives me nitrox for a good price, so why not?) This past winter I did a number of shallower (50-60 feet) reef dives with friends, and we did those dives with EANx 36. Those dives lasted an hour (by captain's orders), and when we reached safety stop depth, my friends' computers started counting off their safety stops. The surfGF reading on my computer was usually 45-50 at that point, meaning we were only about halfway to the highest safe pressure for surfacing when we started that safety stop. I stayed with them for those stops, of course, but they were completely unnecessary except for the fact that their computers were requiring it.

I like this approach, however the better question for most recreational divers (that probably don't own Shearwaters or the equivalent) should be when not to do a safety stop. I'd say go read stories about all the people that got bent and plan to not do what they did.

If you polled all the people that got bent I bet most if not all didn't set out that day to get bent (although I'm sure there are some crazies among us!). Can you skip the SS? Sure. Should you? I'm not so sure (not singling you out @boulderjohn, I'm just saying in general). For most people a SS is a good thing.

Edit: should also add I don't SS if staying above 30'

 

[Bigbella]

When I replaced zincs, as a kid in the local harbor, I didn't bother with safety stops, since the depths were so very shallow; the dives, typically brief; but any dive below, say, ten meters, warrants at least a three minute safety stop, in my mind; and I'll even stop, after doing anything particularly strenuous, anywhere above the red 5 meter "safety stop" hashmark on my old analogue gauge.

Now, in my fifties, I observe every stop; typically remain submerged afterwards; and swim back to shore (where feasible), until I reach a depth, almost shallow enough to stand.

Over the last several decades, I've known three divers who developed DCS, even though they observed every protocol, during their obligative decompression stops, while wreck diving -- one, on the Andrea Doria; and a fourth, whose knee suddenly collapsed while playing soccer with his kids, due to dysbaric osteonecrosis.

I would encourage any and all to do most anything and everything to ensure against future neurological surprises; or, walking with a pronounced limp . . .

 

[Celt]

Stopping below 20 feet on a NDL dive is a waste of time and effort. I could see some benefit to a controlled assent to 20 feet and a slow rise to a 10 foot ceiling with a 3 minute stop for the sake of good practice to gain control where the greatest pressure change is.

 

[wnissen]

I like this approach, however the better question for most recreational divers (that probably don't own Shearwaters or the equivalent) should be when not to do a safety stop. I'd say go read stories about all the people that got bent and plan to not do what they did.

That's a good point, the question should be, under what circumstances do I skip?

 

[Bigbella]

Stopping below 20 feet on a NDL dive is a waste of time and effort. I could see some benefit to a controlled assent to 20 feet and a slow rise to a 10 foot ceiling with a 3 minute stop for the sake of good practice to gain control where the greatest pressure change is.

Regardless, most computers that I have seen or used, since the 1980s, call for a three minute stop at about six meters, once you've reached, say, ten -- a NDL depth, in and of itself, according to my old Suunto, on a first dive. I'd also rather swim below, back to shore, than take a surface swim, through the swell, any day . . .

 

[Stoo]

For the first 25 years I was diving, safety stops hadn't been invented and I don't recall many people getting bent. My approach is that if I am remotely close to the NDL I will do one. And by remotely, I mean remotely.

But as others have said, if I'm putzing around in 20 feet of water, I'm not going up 5' and waiting for three minutes.

On the other hand, regardless of the profile, I surface very slowly, and that wasn't always the case.