Square scrubber and hypercapnia

[davehicks]

I dove the Sport Kiss for about 8 years. I did a few dives to the 150' range and one to around 175' on air. No problems. The only time I had a CO2 hit (in maybe 500 dives on the unit) was an ordinary dive to 70f in 10c water. It was the second dive on the scrubber, after a previous 60-minute dive to no more than 85 feet.

What I believe caused the CO2 hit was driving about 4 hours/250 miles between dive 1 and dive 2. Dive 2 was the following day after Dive 1. I started the dive normally, dropped to 70ft within a few minutes and pretty quickly started getting symptoms. I had a lot of anxiety and irritability for no good reason. I noticed my breathing rate was getting high and realized that I might have a CO2 issue. I bailed out to the BOV first then the stage bottle. I got myself composed, signaled to my buddy, and we ascended normally.

I suspect strongly that some channeling occurred between dive 1 and 2. Probably there was some clumping due to moisture in the sorb and the drive resulted in some settling and channeling across the two lobes of the scrubber.

It's not uncommon at all for me to pack the unit and then drive 100-400 miles before I get to my dive destination. But this was the only time that I did it on a partially used scrubber. Combined with the not-great design of the Sport Kiss scrubber, it did not work out so well that time.

I now dive a KISS Spirit (aka back mount sidewinder) and must have close to 1,000 dives on that unit. I've never had another CO2 hit. Despite driving all over the place with a once or twice dived scrubber in the back of the car.

 

[Wibble]

On the recent episode 84 of the Speaking Sidemount podcast about the forthcoming "Sidewinder 2", the guy mentioned that the (square) scrubbers should be transported vertically to avoid this 'sorb settling issue.

Would that make sense for the Sport Kiss?

 

[Marie13]

On the recent episode 84 of the Speaking Sidemount podcast about the forthcoming "Sidewinder 2", the guy mentioned that the (square) scrubbers should be transported vertically to avoid this 'sorb settling issue.

Would that make sense for the Sport Kiss?

The Sport is a backmount rebreather. Just seat belt it into the car and that will keep it upright. I transport my Spirit that way.

 

[sprockjohnson]

Fresh packed scrubber before the 100 mile drive to the spring during which it was upright. Mushroom valves were sealing like they should. Also, I was using a DPV so no real workload to speak of. I initially suspected channeling but, based on the WOB of this particular unit, am leaning towards bad planning on my part in regards to gas density and narcosis at depth.

 

[Dave1w]

The Sport scrubber isn't the best in the world (although I loved mine as my fist CCR). Also if you have the old Kiss BOV, take alook at that as it has this huge bobbin thing in the middle that restricts the gas flow as well. I used to force the sorb into the corners with my fingers and just take more time packing it. When I upgraded to the classic I could certainly tell the difference, and again when I went with a different BOV. 160 odd feet on a not so great scrubber is possibly your problem.

 

[Jona Silverstein]

I have had a sport for quite a while and between diving myself and talking to Mike. those units really shouldn't be pushed past 100ft without some amount of helium. Out of the 5 units on my shelf, the Sport breathes the worst no questions asked (and there's a unit in there with 10# of scrubber...)

For packing that scrubber, I have found the best method is to fill it, tap it, use your finger to physically push sorb into those corners, then throw more sorb on top, tap, and close. Gas will go to whatever position it can so even though there's no **direct** path for that gas in the corners, It will still get there. At depth due to the injection molded composition, I have found that the scrubber will **crush** slightly so if it is overpacked, it will feel like you are breathing through a wall

By your description it sounds like this was NOT a scrubber structure related problem, I would check the DSV and make sure the mushroom valves are doing what they should, there should be no opposing flow regardless of pressure (ie minimal or heavy negative)

The sport is an awesome unit to learn on but if plan on doing any amount of dives consistently beyond 130ft, its time to upgrade...

 

[sprockjohnson]

By your description it sounds like this was NOT a scrubber structure related problem, I would check the DSV and make sure the mushroom valves are doing what they should, there should be no opposing flow regardless of pressure (ie minimal or heavy negative)

The sport is an awesome unit to learn on but if plan on doing any amount of dives consistently beyond 130ft, its time to upgrade...

Agreed and thanks for the reply. I previously replaced the stock BOV which had the fabric one-way valves for just this reason after it was failing pre-dive tests and instead installed an unknown brand DSV which appears to be functioning perfectly. I also have a rEvo which is better suited for the deeper dives but had just felt like using the Sport that day as I hadn't dived it in a bit... And now I know not to use it at that depth. The WOB is truly... less good.