Safety stops? you do um

[notabob]

reefraff once bubbled...
Diving without a dive flag...
I avoid diving with a flag whenever I can. Having seen too many of them used as targets by sailboats and jetskis, I think they generate too much traffic. I also think that they represent an entanglement and task loading hazard that can't be justified by their purported benefit. That said, in shallow water where there is a risk of vehicular traffic that can possibly hit me, I will shoot a marker even if I don't have a flag with me.

A note of caution - you should be very familiar with your local state laws and regulations regarding diving. A number of states have laws requiring the use of a dive flag. I know Massachusetts is one of them and there are others. And yes, you will get fined if a warden catches you getting out of the water without one. And so will the boats that get within 100ft of a flag (assuming they're caught, of course). This said, I've seen plenty of divers who will still ignore the regs and dive without a flag and fishermen/lobstermen that get right on top of a flag and start doing their thing (or worse, harassing the divers by pulling the flags out of the water, cutting the lines, etc.). My feeling is that towing a dive flag is definitely worth the extra effort. And personally, I have never found it to be a major task loading hazard. The spool hangs on your arm and you periodically feed the line/re-wind it as you get deeper/shallower. As for benefits... It's a marker on the surface that lets people know where you are - those on shore as well as your buddy if the two of you happen to get separated (which happens often enough in the poor visibility that is common to the colder waters). And hold the comments about poor buddy techniques, etc. When visibility is 2-3ft or worse, which isn't uncommon after a storm, all it takes is a momentary glance away from your buddy to get separated. Add in a bit of current and things can get even more interesting. If one of you comes up to the surface for a look-see, a flag will give a much better, and quicker, indication of exactly where your buddy is. Here's another benefit, one that I hope no one has to ever take advantage of. It may sound morbid, but consider this. You dive, something happens to you. You don't come up. If you were towing a flag, you may still have the spool on your person somewhere, with the flag attached. Finding a lost diver without a marker of some sort can prove to be rather difficult. This last "benefit" makes it even more important for a solo diver to carry a flag.

-Roman.

 

[MikeFerrara]

Safety stops are never a bad idea. Even if you don't think the dive warrents one going through the motions (stopping during the ascent) will help insure a slow ascent. But...A fifteen or twenty foot dive is a safety stop.

 

[pdoege]

Gives a little extra room in case bad things occur.

However, the safety stop seems to be a decompression stop with a different name. Since I am diving non-deco, I don't think they are necessary.

I certainly wouldn't stay down at a safety stop if air was running out or other badness was occurring.

It's a safety stop, not a mandatory decompression.

Peter Doege

 

[sharpenu]

Interesting that this topic should come up. There was a report recently in Safe Diver (the DAN publication) that discussed the safety stop and ascent rates.

Apparently, testing has revealed that rates in the 30 or 60 ft/min range with a 3 minute safety stop generated more microbubbles than a slow (15fpm) rate with no stop. I dont have the article any more, has anyone else seen it?

As a result, I have been adjusting my profile:
- slow ascent rate, shorter safety stop (15fpm/1 minute stop)
- make sure computer N2 loading is in the green, if yellow, lengthen stop

So, a 60 ft ascent would take 1-2 min at the old rate plus 3 for the stop, giving a total of 4-5 minutes for the ascent.
This way, 4 min for the ascent plus 1 for the stop, total 5 minutes.

 

[Scuba]

The only reason that I am aware of for the recomended safety stop: is for the purpose of decompression.

The phrase "safety stop" was designed for those who like their doze of truth sugar coded.

I agree sharpenu that the latest research data (from what I've read) appear to imply that a slower ascent rate than 30 fpm may be better, especially the last 20 feet or so after the "safety stop."

I now try to ascend those last 15 ft. reeeaaaal slow, and enjoy every inch of it. Lots to see and do as others have pointed out. I'm usually in no rush to end the dive, anyways.

Unlike some divers I've seen who rush to their safety stop, slam on the brakes, look like they can't find anything better to do than hang motionless for what appears to them an interminable 3 minutes, and then rocket to the surface like a Polaris missile. Me, before and after.

One added benefit I've found with respect to slower ascents: I have found that I am less tired after the dive than when I used to ascend faster. Just an unsubstantiated observation.

 

[greg somers]

Safety stops are particularly important on multiple dives where there is a build up of absorbed nitrogen. Also peoples metabolisms differ with the speed that their tissue compartments absorb and off gas nitrogen. I must confess that any dive below 12 metres I don't do a safety stop unless it is the last of a multiple dive and I always do a safety stop on multiple dives. Body fat absorbs nitrogen quicker than other tissues and releases it more slowly so if you carry more weight than that is another consideration.
Cheers Ears
Gasman

 

[Uncle Pug]

sharpenu once bubbled...
Interesting that this topic should come up. There was a report recently in Safe Diver (the DAN publication) that discussed the safety stop and ascent rates.

Apparently, testing has revealed that rates in the 30 or 60 ft/min range with a 3 minute safety stop generated more microbubbles than a slow (15fpm) rate with no stop. I dont have the article any more, has anyone else seen it?

I think that you might be referring to Alet Diver (the DAN publication)... specifically June 2002 issue and the article by Dr. Bennett.

And if that is the article you are referencing then you might have misunderstood it somewhat. What the article was saying is that a slow linear ascent (ala Hill) is not as good as an ascent with discrete stops (ala Haldane.)

Further the article points out that deeper stops are to be preferred as the 30 fpm ascent from 100' to 10-20' is essentially a Hill table, ie. linear ascent even though it has the three minute stop at the end.

That is why some of us do one minute stops at 30', 20', 10' even though the theoretical tissue compartments appear essentially identical to the single 3 minute stop at 15' when run on decompression software using the ZH-l16B algorithm.

Hill's goats died.

 

[mer]

sdexcalibur once bubbled...
SSI book says you should do a 3-5 min. safety stop at 15 feet.
The past 5-6 dives been about 15- 25 feet. should I be doing them? When do you do them and how long are you under before you will

The SSI dive training manuals also say that this stop is "recommended on all dives over 30 feet." So by the book you don't need a safety stop on dives of 15-25 feet.

This is also the same rule that my dive computer goes by (Suunto Vyper); if my max depth is less than 30 it doesn't ask for a safety stop. Then again, I normally do shore dives, so the safety stop time (for dives 30+ ft) normally just ticks away while we are swimming back in (underwater) to the beach.

Dive Flags

notabob once bubbled...
I've seen plenty of divers who will still ignore the regs and dive without a flag and fishermen/lobstermen that get right on top of a flag and start doing their thing (or worse, harassing the divers by pulling the flags out of the water, cutting the lines, etc.).

The spool hangs on your arm and you periodically feed the line/re-wind it as you get deeper/shallower.

I'm a big fan of the dive flag, but try to avoid putting my arm through the flag reel, unless I REALLY need both hands. The combination of aggressive/territorial lobstermen and a dive flag stuck on my arm is not pretty if said lobserman decides to pull up my flag or manages to tangle the line on his prop. The last thing I want is to make a speedy ascent because a lobsterman or a jetski and tangles my flag. Therefore, I hold mine in my hand most of the dive, since it's easy to let go of.

In terms of task loading, my biggest difficulty is ascending slowly when flag wrangling. It's just something you need to be conscious of... and not get preoccupied reeling in that you forget to monitor the ascent rate. Practice makes perfect however... and my computer yells at me when I get it wrong.

 

[Curly]

...allows me to stay under that much longer! Plus, it's a good buoyancy exercise.

 

[bwerb]

I love being underwater and try to squeeze every minute out of it. I like doing the "hovering guru" move with crossed legs holding onto the tips of my fins while practicing buoyancy control and looking at the fish (when available, results may vary )