Yes, precise circumstances matter.
For nitrogen asphyxiation in general, you do not have to be calm and cooperative for it to be painless, any more than you do so to stand in a room or sit in a chair.
As to the specific setup that the government chose, I can’t vouch for that.
Accepting that you have limited power, choosing an issue, and acting locally has become a lost art. People would rather bitch about how it should be different.