I'm sure you know but PSA for those that don't: N2O is practically the only "safe" inhalant. Others, like gasoline, computer duster, urinal pucks, etc. have a risk of causing spontaneous heart attacks even in young healthy users.
N2O's main physical risk is B12 deficiency, or asphyxiating if you use a mask.
In addition to the risk of sudden death, even on the first use, they cause permanent brain damage with each use and regular use will reduce you to a gibbering shell of yourself from which you cannot recover -- and then you'll probably die. Recreational use is incredibly dangerous and this is one category that you should probably put into the "never use" group. Much worse than any common recreational drugs, including the ones usually demonized by society such as heroin.
With fentynal getting into everything I'd say it's far more dangerous to take a substance orally or by injection that it is to inhale nitrous oxide which fentynal can't get into
I read that the feeling of needing to breathe is actually triggered by CO2 buildup, not oxygen deprivation. So if you breathe pure N2O, you might lose that warning that you need to breathe oxygen. When I played with N2O, I noticed that the high was more intense if I rebreathed or otherwise deprived myself of oxygen. And it also would cause cognitive issues in the weeks after taking it, probably due to oxygen deprivation. I stopped taking N2O after that.
N2O's main physical risk is B12 deficiency, or asphyxiating if you use a mask.