[BwanaNdege]

“Dry ice was apparently extremely effective in killing rats in their nests.”

While I’m neither a ‘Rat not do I play one at the voting booth, I can attest to the effects of CO2. I was in the bottom of a 7-story tall cavern working on a hydroelectric turbine when I was overcome by CO2, probably from welding gases, and hauled off to the hospital with my eyes rolled back in my head (or so I was told). CO2, being heavier than air, accumulated in the lowest point of the project.

[5th MEB]

Pretty much the same thing happened to me.
I was given a tank of what I was told was compressed AIR, I had to use it on an asbestos abatement job in a small boiler room.
I had completely taped off the boiler room to prevent contamination of the outside air and got to the point of having to use the “compressed air” to blow out some areas that couldn't be reached by hand.
Started getting tired and labored breathing, first thought I was just getting to old to do this crap anymore, then realized I was not getting enough oxygen.
Ripped the tape lines off the door and figured f#ck contaminating the outside air, I ain't going to die in this damn boiler room.
It was Saturday morning so I knew there wouldn't be any people around to expose to airborne asbestos fiber.
Monday morning I had a long discussion with HVAC shop foreman about cylinder identification and contents.
His excuse was it was an older cylinder and he didn't know what was in it, not good enough.
I ordered him to dispose of all unidentified cylinders and and replace them with cylinders that were clearly marked.