[Delta 21]

Nitrogen gas asphyxiation is the cheapest, most effective quickest, most “humane” way to kill any mammel.

[P-Marlowe]

Actually pure nitrogen is much more expensive than CO. With CO you can just hook a garden hose to an old V8 engine. You don’t even need an air tight chamber. You can use an old car and just roll up the windows.

[zeugma]

Nitrogen gas asphyxiation is the cheapest, most effective quickest, most “humane” way to kill any mammal.

IMO, the only reason it's not universally used in this country is because it is not emotionally satisfying enough.