I posted this earlier and I'm reposting for any new visibility. I have tried the suggestions but still get dry ice on my regulator during the euthanization process. My process is as follows; 10 pound CO2 tank in an insulated cooler with additional towels wrapped around it. it is in a milk crate attached to the bed of my truck. I run the hose into my 189 liter chamber and pump 12 lpm in for 16 minutes. I then dial back to positive pressure for an additional 16 minutes. Around the 4 minute mark i see ice starting to form on the regulator. By the end of the initial 16 minutes, it appears like there is dry ice in my hose. The regualtor output needle jumps. I do drive job to job while this process is taking place but it does not seem to matter.

Any more suggestions on what I'm doing wrong would be appreciated.

https://trapperman.com/forum/ubbthreads.php/topics/8329792/2

Here’s the old thread so folks don’t have to search!

So working off the pressure drop causing a decrease in temperature theory:

You mentioned that the full tank doesn’t freeze up. Have you found this to be generally true?

If you need 1lb of CO2 each time and often do 4 a day, you’re really emptying a tank. I suppose the first thing to verify is that you are getting a full 10lbs of gas in your tank. It seems like there’d have to be some room for expansion? Maybe 9lbs of CO2? If you’re not getting 9, the % drop is much greater!

1/9 is 11.1% of tank volume used
1/8 is 12.5%
1/7 is 14.3%
1/6 is 16.7%

Total 54.6% of the tank is used up in 4 uses. Where the use on the full tank doesn’t drop the psi much, each use after that really increases the weight taken out. That will really lower the psi on the tank, lowering the temperature of the gas and causing any moisture to freeze.

If you went to a 20lb tank:

1/18 is 5.6%
1/17 is 5.9%
1/16 is 6.3%
1/15 is 6.7%

The tank is used up much slower. The PSI will not drop as fast in 4 uses, so temperature will not go as low. Eventually it will, but you’ll have a much longer trouble-free period.