To Use:
If I found all this on the internet, I'm sure you can, but maybe these will address a few of the questions I've encountered here.
Start by sitting upright in a chair. My understanding is that you should not be lying down, and that you want to be confident you won't fall over when you black out, as any final twitching with your head rumpling the bag against whatever you are lying on might displace the bag enough to allow the inert gas to escape.
I have heard fears of convulsions with this method, but I have also heard —more plausibly— that accounts of convulsions are more accurately associated with sedated-suffocation (a predecessor to this inert gas technique) rather than to inert gas asphyxiation. However, a few final twitches are possible as the electrical activity in the brain fades, and it would be tragic to have the attempt ruined by not taking the simple precaution of being sitting up and stable.
To feel confident that any post-mortem twitching will not knock the cylinder over and jerk the tube out of the exit bag, secure the cylinder to the leg of your chair. I use a piece of webbing; duct tape or a length of cord would work.
If you wear glasses, as I do, remove them. They will be a hindrance when you need to pull the gas-filled bag down over your face, and will allow space for air to remain in the bag.
To pre-fit the drawcord, pull the bag down over your head and face. Tighten the elastic drawcord around your neck so that it's snug, but not cinched tight. You should be able to fit your fingers under it.
Lift the bag up off your face so that the drawcord is now around your temples and just above your eyebrows, below your ears and around the back of your neck, like a shower cap. After adjusting the drawcord to your neck, it will feel tight around your head; this is good.
Scrunch ALL the air out of the bag. The more air you can remove, the faster the inert gas will take effect. If you ignore this step, your attempt will likely fail.
At this point the end of the hose should be inside the bag. I have long hair, so I secure the end of the hose at the back of my head with a hair elastic. Others have taped the end of the hose securely to the inside of the bag with more micropore tape.
If you have long hair, like I do, make sure it is bundled up inside the exit bag, not sticking out under the drawcord.
With the regulator closed, open the valve of the cylinder. There will be a sharp hiss as the regulator fills.
Open the regulator and adjust the flow of gas to 15Lpm. The gas flowing through the tube was surprisingly loud to me, and a bit distracting. Someone here kindly recommended earplugs, which I may do on my next attempt. Or I may listen to music; I doubt earbud wires will displace the drawcord.
The bag will gradually inflate above your head. It will take a minute or two to reach full inflation.
As the bag is inflating, take deep breaths, exhaling fully, to purge as much CO2 as possible from the depths of your lungs.
When the bag is inflated and you're ready, exhale as completely as possible and hold your lungs empty. Slide the bag down over your face and settle the elastic comfortably around your neck. Finally, inhale as deeply as possible; breathe slowly and deeply.