If this is reliable, it might just be the easiest method ever. I use baking soda a lot for cleaning and I add lemon juice (or vinegar) to it when I need to scrub something particularly stubborn. The reaction is instant and I don't think there's any need to wait for the mixture to produce enough CO2 or anything. If I knew the exact doses I wouldn't bother with complicated gadgets and procedures. All I'd do is lie down and put a plastic bag over my head, dump a box of baking soda in the bag, add a cup/bottle of vinegar, and immediately seal the bag with gorilla tape. If I were worried about suffering while I wait for the concentration of CO2 to become strong enough to knock me out, I might just hold my breath for as long as I can. I figure the more baking soda and vinegar you use, the quicker the process. Both are so cheap, I would be overjoyed if this actually works.