I am solidly against executions and quite aware of the moral dilemata.
I was just on about how easy it actually would be.
Why not carbon monoxide?
Short answer, it’s flammable and dangerous to the people performing the executions. That’s why nitrogen is a decent possibility for something like this, it is inert, common, and can be acquired and vented away with little issue.
Tbh, I don’t think that’s an issue. Carbon monoxide is used in slaughterhouses worldwide. You’d think if it’s safe enough to handle for unskilled workers at industrial scale that a few highly paid executioners could use it without blowing up the complex.
Case in point: even the nazis managed to handle it at industrial scale 80 years ago. And their budget for an execution wasn’t remotely as high as the US has.
I mean, it’s probably not as sexy, because it directly shows how straight-up evil the practice of state-sponsored murder is (you know, using the same methods as literally the Nazis did), but then again, if you are a murder state, you are already past the point where you had a right to discuss ethics and morals.