CO2 build up during 65m (210 ft) dive.

[beester]

New parts do not always guarantee good parts. Since they were recently serviced I would carefully inspect them again. More than the usual quick check.

Not recently, months ago. I've done at least 25 dives on the unit since replacement, 15 of them deep.

Anyway I'm happy for all the suggestions and comments. I keep all the options open so I'll double check the mushroom valves.

 

[kensuf]

I'm using the standard JJ DSV. (no golemgear or other reg). So the simplest of designs. There is no way to install the flapper valves the wrong way in this device, and I have checked the loop (sucking it vacuum 1 side and blowing it up other side).


View attachment 734027

The water temp was 12 degrees at the bottom (65m), with a first thermocline around 40 ish meter ( to 14 degrees), and then steadily going up to 24 degrees at 6m. So big difference in temp depending on depth, but not super cold.

Cold impacts the scrubber.

 

[barth]

I wasn't there when you made the dive. But I also had CO2 problems, maybe it was caused by same problems.

I was already exhausted when I walked to the Eastern Scheldt with my GUE CCR, DSLR, deco stage + video ligths. Underwater there was a lot of current. Although I had a new scrubber my breathing was too high. Try not to start the dive until you have calmed down and don't continue (like I did) if there is an issue.

The last time I was underwater with a hammer and saw, I was with a team of 3. I was glad we weren't with a team of 2. Make sure you limit and vary the work underwater.

(A cold scrubber is less efficient.) A scrubber that has been partially used captures less CO2. A high respiration rate ensures a short reaction time of scrubber and CO2. A new scrubber is recommended for a technical dive, a scrubber is less efficient for a deeper dive.

Fitness is important, with a good condition you are less likely to get exhausted.

I think it is a combination of several factors that has caused CO2 problems for you. I'm not sure which factors.

 

[doctormike]

Great writeup!

I also had what I believe was a hypercapnic episode last weekend on my JJ… see if you think this sounds like the same issue.

I’m very compulsive about scrubber packing and mushroom valve checks. Doesn’t mean that a breakthrough CO2 hit is impossible, of course.

This was a cold water NYC area wreck dive, second one of the day, first dive with a minor amount of deco. This was a working dive - I was doing shipwreck photogrammetry, which involved me basically being an underwater tripod, taking thousands of photos of the wreck at fixed distances and depth.

I was at 80 feet, about 20 minutes into the second dive, with about 80 minutes on the scrubber. There was one point on the wreck where there was a very strong localized current, and it was VERY difficult to hold position in that area, especially within the project requirement window. I worked for a while holding the camera stable and kicking hard against the current, finally gave up and swam to the wreck to get out of the current and stabilize. Felt winded, but was able to continue on to other parts of the dive after resting.

Soon after, I started to get a little headache, which became worse and worse over the rest of the day. By the time I got home, it was pretty severe, with no other symptoms of illness. It resolved over a few hours.

I figure I was overbreathing the scrubber. I have heard that CO2 headache can last for quite a while after you have blown your CO2 levels back down to normal, due to changes in cerebral blood flow.

I don’t think that I had a breakthrough from scrubber or loop failure. In retrospect, there wasn’t a time when I felt the need to bail out or even do a dil flush, the headache came on after I was already feeling and breathing normally again.

What do you think? Same issue? Should I have bailed out?

 

[davehicks]

There does not seem to be much of a mystery here. A deep dive involving some medium-heavy work was executed on a scrubber that was over 50% spent. The scrubber was over-breathed and resulted in some CO2 build up. Once the loop was flushed and a resting state restored the scrubber was able to keep up.

Planning a working dive at depth with a half-exhausted scrubber is likely not a good idea. Even with a fresh scrubber it is important to not overexert and take rest breaks you do start working too hard. Huffing and puffing don't mix well with CCRs.

 

[davehicks]

Great writeup!

I also had what I believe was a hypercapnic episode last weekend on my JJ… see if you think this sounds like the same issue.

I’m very compulsive about scrubber packing and mushroom valve checks. Doesn’t mean that a breakthrough CO2 hit is impossible, of course.

This was a cold water NYC area wreck dive, second one of the day, first dive with a minor amount of deco. This was a working dive - I was doing shipwreck photogrammetry, which involved me basically being an underwater tripod, taking thousands of photos of the wreck at fixed distances and depth.

I was at 80 feet, about 20 minutes into the second dive, with about 80 minutes on the scrubber. There was one point on the wreck where there was a very strong localized current, and it was VERY difficult to hold position in that area, especially within the project requirement window. I worked for a while holding the camera stable and kicking hard against the current, finally gave up and swam to the wreck to get out of the current and stabilize. Felt winded, but was able to continue on to other parts of the dive after resting.

Soon after, I started to get a little headache, which became worse and worse over the rest of the day. By the time I got home, it was pretty severe, with no other symptoms of illness. It resolved over a few hours.

I figure I was overbreathing the scrubber. I have heard that CO2 headache can last for quite a while after you have blown your CO2 levels back down to normal, due to changes in cerebral blood flow.

I don’t think that I had a breakthrough from scrubber or loop failure. In retrospect, there wasn’t a time when I felt the need to bail out or even do a dil flush, the headache came on after I was already feeling and breathing normally again.

What do you think? Same issue? Should I have bailed out?

I think you did the right thing. You didn't need to bail out after a loop flush.

Many years ago, when I have a newish OC diver, I started trying to extend my dive time slowing my breathing too much. I ended getting monstrous bad CO2 headaches until I learned proper breathing technique. They last for several hours and fade away after a bit.

 

[doctormike]

I think you did the right thing. You didn't need to bail out after a loop flush.

Many years ago, when I have a newish OC diver, I started trying to extend my dive time slowing my breathing too much. I ended getting monstrous bad CO2 headaches until I learned proper breathing technique. They last for several hours and fade away after a bit.

Yup, and a big difference between my dive and the OPs was depth (i.e. gas density). His scrubber was a bit more spent than mine as well.

While I'm pretty sure that the headache was a CO2 hit, it's interesting that I didn't really get the classic symptom of rapid breathing that you just can't stop. I still dive a stock JJ DSV (I added a gag strap this year on the urging of Simon Mitchell), but this is the sort of thing that makes me BOV-curious.

 

[Whitrzac]

Did you overbreath the scruber or just the physiology of your lungs and wear yourself out?

Published scrubber duration's(at least the kiss ones) are at depth(high gas density), cold water, and at a higher co2 production rate than any human could maintain for more than a few min.

I can easily reproduce co2 hit symtoms on the surface after getting on my bike for thew first time in the spring after not doing cardio all winter.

 

[beester]

I didn't have any symptoms post dive (headaches or such), but I definately felt winded during the episode and needed to really slow down. My breathing rate increased a lot during the episode.

In any case now I have some practical experience with the CO2 limits of CCR diving vs OC. I'm quite sure that on an OC dive in the same circumstances (depth, workload) I would not have had any real issues.

About when to bail out (question for me but also question from doctormike). That's a nasty one. If your rebreather fails in a number of other ways (PPO2 spike, low PPO2, sensors not in line, excessive water in the loop), it's reasonably clear what's going on and there are a number of ways (which obviously includes bail out) to go about resolving the issue. The point is unless it's a very low PPO2 that you didn't catch in the minutes leading up to it, you have time to evaluate and react PLUS you are not mentally impaired.

With a CO2 hit (I wouldn't call my incident a real hit, but it could have escalated to such), it's much more gray. There are no quick clues (unless a temp stick maybe) that you are overbreathing your unit or you are about to have breakthrough on your scrubber and by the time the CO2 really hits hard you might be so mentally impaired that you no longer make good decisions.

Like I said, my buddy didn't know what was going on (and he's a very experienced RB80/JJ diver), just that I asked him to stop and give me a minute. He checked my hud and controller and saw that everything PPO2 wise was well so he didn't really capture the issue. IF I had not settled down, or the CO2 build up was not washed away, I could have easily ended up in a state where the CO2 build up was such that I could no longer make the right decision to bail out.

So my take aways after listening to all you is:
- New scrubber when doing working dives at depth
- regularly pause during work and self evaluate (awareness)
- Brief on the CO2 topic with the team/buddy before dive (the additional risk of CO2 build up)
- Bail out sooner rather than later. In fact CO2 build up is one of the only real reasons to quickly bail out at depth (the other being super low PPO2).

 

[jale]

So my take aways after listening to all you is:
- New scrubber when doing working dives at depth
- regularly pause during work and self evaluate (awareness)
- Brief on the CO2 topic with the team/buddy before dive (the additional risk of CO2 build up)
- Bail out sooner rather than later. In fact CO2 build up is one of the only real reasons to quickly bail out at depth (the other being super low PPO2).

Hi
Thanks for sharing but I am a bit annoyed by your conclusions.
Indeed, aren't these points normal and obvious procedures?
Do you mean that GUE doesn't ingrain the obvious?!