There is a fair level of technicality and details involved such as using the right regulator, flow meter, flow rate etc. One needs to put enough effort and research into it to get it right.
I 100% agree with
@Diver_K_A! There is a good thread somewhere here. And, I highly recommend the book mentioned in the Wiki called
Five Last Acts – The Exit Path (2015 edition): The arts and science of rational suicide in the face of unbearable, unrelievable suffering 2nd Edition by Chris Docker.
His first chapter is on the inert gas method and covers it very thoroughly. This is where I got all the info I needed for my primary method. I'm all set-up and feel very confident in it.
As an alternative for you, if you can't source the gas, perhaps "night-night" (neck compression = like hanging but without the discomfort of having to support the weight of your body by your neck): https://sanctioned-suicide.net/threads/the-night-night-method-mega-thread.6834/
In the book I suggested, chapter 2, Docker spends 80 pages on this = "compression" and it is also very well written (the whole book is). Here's the first paragraph:
Compression is a simple method of self-deliverance that relies on no complicated equipment and does not require drugs. The main veins and arteries of the neck are compressed in such a manner that the pressure remains after the person has fainted. Fainting, and death, is a result of lack of oxygenated blood to the brain. It is very quick - fainting occurring within a minute and death following within a few minutes. (In rare cases, death may be accelerated by cardiac arrest after loss of consciousness.) One of the main methods of achieving compression is to use a tourniquet around the neck, carefully positioned so it does not obstruct breathing. Another method is to use continuous looping, and a third is the introduction of mechanical devices [aka a "hookless" ratchet tie-down... those are available ~everywhere... usually used secure a load in the back of a pickup truck, e.g.]. Some momentary discomfort is possible, but brief, and can be minimized with careful forethought.
You quickly faint, while continuing to breathe normally. Death is caused by depriving the brain of oxygenated blood....
The hookless ratchet tie-down compression method is my personal backup method. In my careful, brief "testing", the feeling of the strap/tourniquet on my neck gave only minor discomfort. Got one in a drawer 10 feet from me right now. Total cost ~$10.