I recently decided that I am morally opposed to "whacking" rats and decided to build my own CO2 chamber. I first tracked down a refurb 10 lb. canister. I found a wonderful supplier in Waterloo that let me have one (filled) for $100 with the hose valve hookup.
I then went to Home Depot and picked up a 5/8" hose (10 feet for $6) and a pair of circle tightening thingies (that's the technical name folks) for each end of the hose ($3). I also picked up a connector for the rubbermaid ($3). I drilled a hole about two inches up on the bottom of a tall #2220 rubbermaid ($6) and attached the hose to the connector with the clamp.
Lastly, I attached the hose to the valve at the canister and tightened it with the last clamp and tried it out. Works great. I can euthanize approx. 15 ~100g or so rats at one time or 5-7 large adults in under one minute. I was told I should have close to 150 uses from a single tankfull. Refills are $16. Total cost: $118.
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