[cymbeline]

“See #58 on this thread “

I imaging there are plenty of gasses that will painlessly kill someone but beginning with a quick put-to-sleep would mean less of a torturous wait to the executee.

[zeugma]

Yes, but if you simply use nitrogen, you are using a completely inert and harmless gas, which is why it can be safely vented directly to the atmosphere afterwards. In industrial settings where there is a potential for nitrogen leaks, OSHA requires all kinds of safety protocols be in place. That is because you can walk into a room that is filled with pure nitrogen, and you won't even realize you are suffocating. You will simply drop and die without even knowing you were dying. 78% of every breath you take is nitrogen. The body simply doesn't react to it. The suffocation reflex is triggered by an excess of CO2, not the absence of oxygen. Nitrogen is the perfect thing to use for executions.