Questions about the 3 min safety stop....

[ivobj]

With the dive profile you described, although you would benefit from it, you defintely don't need it, as long as you ascent slowly.

 

[Cave Bum]

My question regards the three minute stop at 15 feet in the setting of recreational, no decompression diving... Yesterday my wife and I did a 40 minute dive. Most of it was in the shallow zone of the quarry at around 30-35 feet, working on skills, doing the swim throughs, etc., and then we made one short descent to around 70 feet. I.e., we were very much within the safe no decompression limits. Later my wife asks me, “If we were so much inside of the safe no decompression limits, why did we have to do the 3 minute safety stop?” (Now let me say that neither of us is in any way against hanging out at 15-18 feet for 3 minutes!) However, I could not give a concrete answer and so I am asking for input.

Not sure who your certifying agency is but with PADI tables only the bottom 3 pressure groups (2 shaded and 1 black I think) require a safety stop.

It is, however, good practice, if nothing else, to do them anyway.

Be safe and have fun in the water. Bruce

 

[Blackwood]

This "Golden Rule" was pulled out of thin air by the founding gods of recreational diving. It was born around a table littered with beer bottles and late night after-dive yacking.

Absolute fact... but not science.

Correct. I forgot to append the standard "this is all just theoretical modeling" disclaimer.

Everything I said above refers to satisfying a model, not the actual processes within the body.

Did you plan the dive on the tables? Assuming you're PADI, the RDP is quite clear about when a safety stop is *required* and when it's *optional*.

Not sure who your certifying agency is but with PADI tables only the bottom 3 pressure groups (2 shaded and 1 black I think) require a safety stop.

Even when the RDP's instructions require a "safety stop" for within-NDL dives, its decompression model does not. It's after-the-fact padding since decompression is all shades of gray anyway.

(BTW Cave Bum, your avatar is missing some parenthesis)

 

[Buoyant1]

I just think it's a good habit. When we dive locally, we do our deeper dirty work, then hit our 15-20 ft. for three minutes before going over the road to the shallow part of the quarry, and doing about 10-15 minutes of 6-10 ft. We really don't need the safety stop, but we take it as an opportunity to do "S" drills if you are configured that way, or practice deploying a long hose, or changing to a pony rig or whatever you feel the need to work on. Some of us just try to work on hovering. (other people have made rock sculptures!) Given the time and gas, you may as well...it beats getting out of the water with 1000+psi!

 

[Teamcasa]

.. my wife asks me, “If we were so much inside of the safe no decompression limits, why did we have to do the 3 minute safety stop?” ... I could not give a concrete answer and so I am asking for input.
...As you get near to decompression limits but still within the no-deco range, does the safety stop serve as precautionary but non mandatory decompression stop?

The stop is by definition not mandatory unless your dive profile indicates different. The point of a safety stop is to give your body a chance to eliminate excess Nitrogen loading.

For me, making a super slow ascent followed by a 3 minute stop helps keep my buoyancy skills sharp, allows me time to secure any gear (video camera, lights ect.) and get ready to surface. I also think making a slow ascent helps reduce post dive fatigue, but I have no hard evidence for that assertion.

On those dives where I approach my NDL, I make it a point to extend my safety stop until I run low on air (300psi) or until my computer displays a noticeable reduction in Nitrogen loading.

I dive for fun and getting bent is not part of my dive plans so I ascend slowly and take my stops seriously.

 

[Cave Bum]

(BTW Cave Bum, your avatar is missing some parenthesis)

Hummmm? Looks right to me...

Thanks for letting me know, I fixed it.

 

[tc]

Probably the single biggest benefit of the safety stop is getting folks to slow their ascents and stop just before going into the portion of the ascent with the greatest pressure change.

 

[Blackwood]

Hummmm? Looks right to me...

Thanks for letting me know, I fixed it.

There's nothing wrong with a MOD for air (computed for 1.6) of -25 feet, right?

 

[Teamcasa]

Probably the single biggest benefit of the safety stop is getting folks to slow their ascents and stop just before going into the portion of the ascent with the greatest pressure change.

I'm with you on that Tom. Just knowing I have a target depth to stop at does make the ascent rate a little more important.

 

[BobinNC]

DC53, if you are a DAN member they offer some really good online seminars for free and at least one them that I did had a history of decompression theory. It was very interesting and to see all the fatalities that happened before we understood physically what was happening to our bodies, we owe a lot to those who went before us. The seminar was also very informative on dive profiles and the effects on the body. I think even if you are not a member you can do the seminars but they cost a few dollars then.