Popped up too fast from safety stop

[larch]

Hello - I am a new diver (14 dives over 3 trips) and today made a rookie error as I had some air left in my BCD while ascending and waiting at the safety stop (I was holding on to a line so was able to stay at 5m even with air in the BCD). After completing the safety stop and letting go of the line I popped up to the surface very quickly. I am wondering if there is any significant safety risk with "popping" up quickly from a safety stop? I definitely ascended too quickly, but only from 5 meters and after the safety stop. I was with a divemaster and he commented on my popping up but didn't imply there was any serious issue with what I had done (in terms of looking for DCI symptoms, etc). It was the first of two dives today and I did 2 dives yesterday...nothing more than 18 meters. I am planning on 2 more dives tomorrow.

(I have only now become a little paranoid after feeling extra tired and a little woozy the rest of the day...but that could be due to a long walk in the sun, ice cream for lunch, etc).

Lesson learned to remember to dump all air!

Thanks!

 

[JackD342]

The greatest concern is lung expansion injury if you are even slightly holding your breathe on that ascent. And do not minimize by thinking it is “only” 15 feet. Pressure differential per foot is greater at shallower depths.
Having said that, pay attention to what your body is telling you and call DAN or seek medical assistance if you think there is a problem.
Also, do not over compensate your correction of this problem on your next dive. Do NOT dump ALL air. Release what you need to as you ascend to remain neutrally buoyant or slightly negative as you swim up. Sounds like you were at the other extreme on this dive, relying on a firm grasp of the line to hold you down. This is not an all or nothing equation.

 

[larch]

Thanks for the quick response - all makes sense and I got myself a refresher on Boyle's law reading up on it. I'm about 8 hours post dive (since completing the second dive) and no clear symptoms as I read what they would be. Will certainly be aware and talk to the dive manager tomorrow just to be sure. I think a lot of water and a good dinner may do the trick after a hot, long walk this afternoon.

Noted on not overcompensating. On the 2nd dive I was much more aware and dumping along the way and had emptied the BCD by the safety stop - and swam slowly to the surface after the stop with no air in the BCD.

 

[ontdiver]

These are good learning experiences, even though it may throw you off for a day or so. Buoyancy control is not easily mastered but you don't want to obsess about it either. But once you nail your skills down it will become second nature. Keep diving and keep having fun.

 

[flyboy08]

Practice your SS without a line.

Use your lungs to accent/descend 3 feet..if you are unable to do so, take a buoyancy class.

 

[Doctorfish]

If you are out past 8 hrs and you are ok, then you are ok. As pointed out, the concern with coming up from a safety stop is barotrauma. If you were going to have a pneumothorax or blown an ear, would have happened already. I've always felt that for beginners, better to be over than underweighted and to let all the air out of BC at the start of the ascent.

 

[scubadada]

and see https://www.scubaboard.com/communit...rst-dive-post-open-water-course.576007/unread

 

[EFX]

I'm glad to see you corrected your buoyancy on your second dive. The secret to good buoyancy and preventing a run-away buoyant ascent is to vent some air from your BCD on the way up. If you stop kicking up and you are already floating up it is too late. Buoyancy changes take a second or two to be felt. That is why it is important to add or vent air in small bursts and wait for the changes to take effect. I'm sure you've heard all this in your OW class. It takes experience to get a hang of it but with more diving you'll get it.

 

[TMHeimer]

Of all the buoyancy stuff I've heard or read about, that's the one---"small bursts". Was told that when taking OW, and it didn't take many dives to get that down pretty well.

 

[TrimixToo]

<snip>
Pressure differential per foot is greater at shallower depths.
<snip>

At the risk of sounding pedantic (who, me?)...

This seems to be a very common mistake, or perhaps it's just a shorthand way of saying that the *percentage* pressure differential increases at shallower depths. The actual pressure differential is completely linear, irrespective of depth. It's about 1/33 ATA (atmospheres absolute, or 14.7 PSIA) per foot in salt water, and 1/34 ATA per foot in fresh water.

For example, ascending from 66 FSW to 33 FSW the pressure declines from 3 ATA to 2 ATA, a 33.3% decrease. Ascending from 33 FSW to the surface, the pressure declines from 2 ATA to 1 ATA, a 50% decrease. But in both cases, the pressure was reduced by 1 ATA.

However, the *volume* differential is not linear and it is greater at shallower depths. This is what increases the risk of lung overexpansion injury and makes bubbles grow faster for a given ascent speed when you're shallower.