ascent rate: how slow is too slow?

[Russoft]

After owning my computer for 2 years, I finally took the time to download my dives and look at my dive profiles. This was prompted by a series of four dives to ~100 ft from my last dive trip, two of which were part of my AOW Deep/Wreck dives. All dives were on wrecks in water with moderate to high current. Consequently the descent took 4 minutes because we were fighting the current the whole way down. For all four dives I found that based on my gas planning and NDLs, I ended my dive and began my ascent up the mooring line at about 17 minutes bottom time. My ascent rate was about 10 ft/min with a 3 minute safety stop. I surfaced with a dive time of 29-31 minutes for all dives. I remember thinking at the time "that's a really long ascent", but it seemed to be about the same speed that other divers ascended so I assumed it was about right.

My question is this: At what point is a slow ascent unproductive? Is 10 ft/min too slow? I can't help but notice it's 3x slower than the recommended ascent rate and it takes 9 minutes to reach the safety stop from 100 ft.

 

[tbone1004]

10ft/min is still making upward progress in a constant fashion so as long as you are heading in the right direction and not stopping, then it won't be an issue. Fast causes problems, stopping can cause problems with slow tissue ongassing, but 10fpm isn't going to be an issue at all, neither is 1fpm, it's just really really slow

 

[Akimbo]

Your computer will account for slow ascent rates. Your are fine as long as you don't run out of gas. Picture diving on a wall. Nearly all of your dive can be ascending.

 

[KeithG]

10ft/min is still making upward progress in a constant fashion so as long as you are heading in the right direction and not stopping, then it won't be an issue. Fast causes problems, stopping can cause problems with slow tissue ongassing, but 10fpm isn't going to be an issue at all, neither is 1fpm, it's just really really slow

Keep in mind that the 30 feet per minute is a recommended maximum ascent rate guideline. So you will want to be slower.

Based upon a recent thread regarding a surprise deco, if your computers NDL is still decreasing as you ascend, then you are going too slow.

 

[rsingler]

What tbone said, with maybe one exception.
If you're doing repetitive dives (like on a trip someplace exotic), and your habit is really slow ascents, then that could come back to bite you. As tbone said, stopping can cause problems with slow tissue ongassing, so that at the 15' to surface transition, you have an excessively high gradient in a slow tissue compartment, and an increased risk of bubble formation.
Search for "NEDU study" and look at some of the deco threads. Although it's largely theoretical for no-stop diving, I can see where after a week of fun, you may have slow compartments that are pretty full. Really slow ascents only make that worse. As you'll discover, the notion of deep stops is now largely discouraged.

Follow your computer. It will generate 30-60 fpm below 60' and 15-45 fpm above 60'. While faster is definitely not good, slower (especially below 60 feet) is also problematic if you already have an N2 load.

E.g., my last dive trip to Bonaire: Two tank boat dive in the morning; back to the resort for lunch; two tank boat dive in the afternoon; back to the resort for dinner; digest a bit; shore night dive off the hotel. Repeat x 7 days. You don't need to be ongassing slow compartments by 10 minute ascents.

 

[Russoft]

As you'll discover, the notion of deep stops is now largely discouraged.

Follow your computer. It will generate 30-60 fpm below 60' and 15-45 fpm above 60'. While faster is definitely not good, slower (especially below 60 feet) is also problematic if you already have an N2 load.

I do remember reading that deep stops are no longer recommended. To my dismay, I noticed my computer recommending a deep stop for 2 min at 50 ft during those dives so I'll need to switch that off (though the computer lets you ignore it too).

What you're saying about different ascent rates at different depths makes sense to me and was something I was contemplating when I asked the question. I really do like to crawl to the surface because I feel better as a result, but I suspected that the slow ascent while still deep was probably giving me a larger nitrogen load (to slow tissues, anyway) rather than decreasing it.

 

[Akimbo]

Although it's largely theoretical for no-stop diving, I can see where after a week of fun, you may have slow compartments that are pretty full. Really slow ascents only make that worse. As you'll discover, the notion of deep stops is now largely discouraged.

Slow ascents aren't the same as deep stops, especially in this context. You can easily take 45 minutes to ascend from 100' to 20' on a wreck, wall, or pinnacle. Continuous ascents during saturation dives are the norm... like 3-6'/hour.

 

[Frackingawesome]

I do remember reading that deep stops are no longer recommended.

Someone should REALLY tell Sunnto... it seems like i do a dive at 30 feet and my computer wants me to decend to 90 for a deep stop(not really, it just seems that way)... and if i dont i get the annoying Exclamation Point of you ****** up...

 

[Alastor]

Almost every suunto capable to compute deep stops have a configuration to disable them - except the Helo2 (If I remember well). So, keeping them off could be an option. For what concerns ascent speed - if you planned the dive, you have also a reference ascent speed - it's part of the planning - and you should stick on it.

 

[MaxBottomtime]

Running out of air before reaching the surface is too slow. Anything else is fine.