It’s been tested on animals. It’s how cattle are often killed these days when we process them for meat. It’s fine.
It was said not to do well on animals. So I say hang him at dawn. They sell quality rope at Ace Hardware.
Makes sense.
Nitrogen and helium are both inert. The Hemlock Society & Final Exit folk have been using helium for years for assisted suicides, so it has an established track record of causing people to fall asleep peacefully never to wake.
What causes distress when you suffocate is the build-up of CO2. CO2 is a waste product removed from the blood by the lungs so you can exhale it. If your lungs are flushed with an inert gas every time you inhale, there’s no CO2 build-up. The inert gas won’t react with your tissues to cause discomfort because it can’t (else it wouldn’t be inert).
If you’ve ever breathed from a helium balloon until you were light-headed (or even passed out) you know the truth of it because people have been doing it for ages and there’s no discomfort. Youngsters at parties have been known to do it for giggles. Using nitrogen for an execution will produce exactly the same effect. Breathe it long enough and you die without ever feeling the discomfort of CO2 build-up.