I'm in Canada (Ontario) too & trying to figure that out.
I'm learning towards CO (carbon monoxide) in a tent cuz before I joined this forum basically a week ago, I was googling accidental deaths & it turns out there's been multiple cases of people dying in their tents when they brought their charcoal grill into their tent to either warm them up or perhaps protect it from rain.
Because it no longer had smoke, they assumed it was fine.
But apparently that's actually when CO is released the most - when the flame dies down.
With minimal oxygen in the tent, the charcoal produces CO instead of CO2 (carbon dioxide).
CO is odorless & doesn't produce the same suffocation feeling as CO2 - and hence why they don't wake up even though they are slowly dying, whereas CO2 would cause the panic feeling of grasping for air. (Sorry if you already know this. )
I thought this method would be ideal because people even accidentally do it.
Apparently it can come with a headache, but if the CO concentration is high enough, then it would happen pretty quickly before symptoms would come up like headache, nausea, etc, which come on slowly with lower concentrations.
However, there have been instances of people that have tried deliberately to CTB as a result of CO poisoning in an enclosed space, & failed - only to have brain injury.
I find it so sad that people can die by accident while camping and yet when somebody actually wants to die and try so hard, they can mess up.
There is a thread on here that I am now following that talks about tent + CO method.
Eg. The tent needs to be adequately unventilated, etc cuz CO that mixes with Oxygen becomes CO2 & sabotages the process.
There's probably more methods too but this is the one that seems to me to be the most painless/peaceful (since one would pass out before they die), time efficient (can be about 15 min if adequately high CO concentration), and cost effective (eg. Tent & grill could be bought off Facebook marketplace, charcoal not that expensive)
Feels so weird that I'm now sharing this kind of stuff with others but I'd want someone to help me as well.
Feel free to let me know if you come across a better method.
I'm trying to figure out how to source SN or argon/nitrogen as well but seems like these are difficult to obtain unless you work in a specific industry.
If I could, I would do the CO method with SN just to try and reduce the risk of waking up.