Ascent Rate (SSI vs PADI)

[dmoore19]

Then I stand corrected. However, if you can disable the function....

The Mares Puck will lock out the diver after a too-fast ascent (and go into gauge mode). It does so when the diver exceeds the maximum rate for a stretch equal to at least two-thirds of the depth at which the audible alarm was triggered. The maximum rate is 39 fpm. The manual mentions an option to disable this "feature."

The Suunto Zoop (and presumably many other Suunto models) will add a mandatory safety stop if you exceed the designated maximum ascent rate, which for the Zoop is 40 fpm momentarily or more than 30 fpm continuously.

 

[Kharon]

To my knowledge no computer will lock you out, it may however penalize you (suunto) on future NDL times for following dives.

I had to check - my Icon HD will lock you out for an uncontrolled ascent violation. It then functions only as a depth guage for repeat dives. This feature can be turned off. Here's their definition:

If the ascent rate exceeds 12m/min (40ft/
min) at a depth below 12m (40ft), the message
on the screen changes to UNCONTROLLED
ASCENT. If a speed in excess of 12m/min
(40ft/min) is maintained for two thirds or
more of the depth at which the alarm was
first triggered, ICON HD considers it a dive
violation and the display will show VIOLATION
- ASCENT.

 

[Steve_C]

You do not want a computer that will lock you out and not have that feature disabled. Stuff happens. I want my computer to always give me some advice be it deco or reduced NDL.

 

[diver 85]

Just stay below your smallest bubbles-------------, had to get it in......

 

[tursiops]

Just a note: PADI does not say to ascend at 60 fpm. They say to NOT EXCEED 60 fpm. I teach -- and execute -- 30 ft per minute in the spirit of a "maximum operating depth" as in PPO2=1.4, with 60 fpm being a "contingency operating depth" as in PPO2=1.6. So we have an operating ascent speed (30) and a contingency ascent speed (60).

If, however ascending from depth (like 130+ ft) I'll exceed 60 fpm up to 60-ft depth, then slow down. The point, of course, is not how many feet you are going in a minute, but what is the fractional change in ambient pressure per minute. 60 fpm means something different at 130 ft than it means at 30 ft.....in terms of fractional pressure change per minute. Ascending 33 feet is an ambient pressure change of 1 ATA, no matter how deep you are. But the fractional pressure change is 1/5 at 132 ft, 1/4 at 99 ft, 1/3 at 66 ft, 1/2 at 33 ft. Now take that fractional change and relate it to 30 and 60 fpm ascent rates....60 fpm going from 99 to 66 ft is the same as 30 fpm going from 33 ft to the surface.

 

[diver 85]

Just a note: PADI does not say to ascend at 60 fpm. They say to NOT EXCEED 60 fpm. I teach -- and execute -- 30 ft per minute in the spirit of a "maximum operating depth" as in PPO2=1.4, with 60 fpm being a "contingency operating depth" as in PPO2=1.6. So we have an operating ascent speed (30) and a contingency ascent speed (60).

If, however ascending from depth (like 130+ ft) I'll exceed 60 fpm up to 60-ft depth, then slow down. The point, of course, is not how many feet you are going in a minute, but what is the fractional change in ambient pressure per minute. 60 fpm means something different at 130 ft than it means at 30 ft.....in terms of fractional pressure change per minute. Ascending 33 feet is an ambient pressure change of 1 ATA, no matter how deep you are. But the fractional pressure change is 1/5 at 132 ft, 1/4 at 99 ft, 1/3 at 66 ft, 1/2 at 33 ft. Now take that fractional change and relate it to 30 and 60 fpm ascent rates....60 fpm going from 99 to 66 ft is the same as 30 fpm going from 33 ft to the surface.

It's all about %s.......But, that's true in all of life..

 

[emoreira]

Just stay below your smallest bubbles-------------, had to get it in......

I second this statement. It was teached in my school. Smallest bubbles ascent slower than big bubbles.
Bubbles ascend at a rate of 20 mts/min (65 ft/min). You should ascend at a lower rate than this. Slower means safer.

 

[DivemasterDennis]

We (a PADI shop) teach 30 fpm ascent rate, which nearly every diver I have ever dove with seems to exceed, especially those last 15 feet. Watch people ascend after safety stop- 9 out of 10 go too fast. I read an article advocating 20 fpm from 60 feet down to the surface, 30 fpm at depths over 60 feet. 10 meters per minute (33 fpm) is my goal and standard. IF you never exceed 60 fpm, and never have your computer flash and squawk due to ascent rate, you are a safe diver indeed!
DivemasterDennis

 

[diver 85]

I second this statement. It was teached in my school. Smallest bubbles ascent slower than big bubbles.
Bubbles ascend at a rate of 20 mts/min (65 ft/min). You should ascend at a lower rate than this. Slower means safer.

It has worked for me for almost 30 years........I'm not gunna fix "something that 'ain't' broken".....lol

EDIT:.....sometimes my Veo 180 doesn't understand it....

 

[DevonDiver]

Slower means safer.

IMHO safety isn't that big an issue (30-60ft p/min) within appropriate recreational depth/time parameters.

That said, there may be cause to identify optimum. Especially over multiple and/or repetitive deep dives - where post-dive fatigue (non-symptomic DCS) may be evident.

Article: Optimum Ascent Speed for Scuba Divers