Safety stop question

[Spencermm]

After reading some of a current thread I have a question.
If you do say a 30-40 min. dive at 20 feet you don't need to do a safety stop because at that depth you have been off-gassing the whole time anyway. Is this correct?
I had been wondering why at my OW check outs, which were on a platform at 20', we didn't do safety stops at the end of each dive.
Thanks for any input,
Spencer

 

[Rick Murchison]

After reading some of a current thread I have a question.
If you do say a 30-40 min. dive at 20 feet you don't need to do a safety stop because at that depth you have been off-gassing the whole time anyway. Is this correct?
I had been wondering why at my OW check outs, which were on a platform at 20', we didn't do safety stops at the end of each dive.
Thanks for any input,
Spencer

No, if your whole dive has been at 20 feet then you've been ongassing the entire dive... but you haven't been ongassing enough to worry about with a safety stop. The top PN2 in your tissues that you can achieve at 20 feet is about 1.25 ATA, which shouldn't promote bubbling with a direct ascent to the surface. However... there is anecdotal evidence that very long dives as shallow as 20' can cause some DCS symptoms, so a leisurely ascent is still warranted... the longer the dive the more leasurely the ascent.
Rick

 

[The Chairman]

Rick is right... it's not that you are off gassing the whole time, but that you have no need for an additional stop. In fact, where would you stop?

 

[Rick Murchison]

Rick is right... it's not that you are off gassing the whole time, but that you have no need for an additional stop. In fact, where would you stop?

Are you sayin' I built a clock when all he wanted to know was the time? My daughters say I'm bad to do that...
Rick

 

[The Chairman]

In your case, that would be a "Grand Father Clock", nes pas?

 

[Spencermm]

Are you sayin' I built a clock when all he wanted to know was the time? My daughters say I'm bad to do that...
Rick

I like clocks and found your answer to be very informative.
Thanks,
Spencer

 

[The Chairman]

Now, now... don't go getting him all wound up! Alarms might go off!

 

[Rick Murchison]

Now, now... don't go getting him all wound up! Alarms might go off!

OOhhhhhh PUNish me!

Good one, Pete!
Rick

 

[The Chairman]

Speaking of stops...

I did a dive in an alpine (7300+ ft) lake last week: Max depth about 18 ft. I was taking pictures for a Scouting event called Powder Horn so I spent much of my time (2.5+ hours) on the surface. The water temp was a balmy 68 degrees and I had a 3 mil full wetsuit on. After the event, I felt a bit chilled,but not too much. About three hours later, I felt I had subclinical DCS. I was "out of it" and felt incredibly lethargic and didn't care about ANYTHING. 20 minutes on Oxygen did the trick. But I have to wonder if this was altitude sickness (my first day at that altitude) or a mixture of altitude sickness and subclinical DCS.

It's episodes such as these that make me realise that we don't have EVERYTHING figured out.

 

[AbyssalPlains]

Are you sayin' I built a clock when all he wanted to know was the time?
Rick

Rick: Maybe. But I can very well relate to you as I am a similar kind of guy. Please don't change anything - your posts are very educating and insightful. The board would be less of an educational resource without your input.