I've tried this method in my small bathroom but didn't get knocked out for some reason. Charcoal was of questionable quality though. Burned 2.5 kg in a large chimney starter. It took approximately 90 minutes till the flames disappeared completely, after which I put the glowing charcoals in a metal container. The charcoal became 1/3 of the amount after burning. I took the metal container immediately in the bathroom since it was no longer emitting smoke. It had terrible additives that irritated my throat. The temperature inside the bathroom got really warm but not to an uncomfortable level. I couldn't manage to properly seal the bathroom cause there are a couple of large cracks but I tried my best to seal it as much as I could. I hoped that the rate of CO production would be enough to compensate for its escape in those cracks. I remained in the closed bathroom for about an hour. I was already dizzy before entering cause I wanted to sleep badly. I didn't take medications or alcohol. I laid there with my upper body elevated to catch the most CO since its lighter than air and concentrates more near ceiling. I don't know how high the PPM rose since I don't have a meter but I got comfortably numb and my visual field started to rotate when fixing my eyes at certain object. I felt kinda high and euphoric.
After about 30 minutes I felt slight disturbances in my heart, like it was murmuring slowly and quietly, but no pain or discomfort. I got more sleepy and wanted to lay comfortably to fall asleep but I couldn't since the space is small and I couldn't extend my legs fully. I was sitting in a very uncomfortable position and it played a certain role why I didn't fall asleep in time. I got very tired waiting for the more dramatic effects to kick in and thought it would take many hours to finish me off had I fallen asleep. I feared that had I remained there and waited, the charcoals would finish burning too early and I would wake up with severe body damage. For that reason I abandoned the attempt and cleaned everything to remove suspicious traces from the bathroom.
What I've learned from this attempt is the following:
1. The charcoal should be of high quality and preferably without additives as they irritate the throat and spoil the peaceful experience.
2. It's better to use a bit larger and well sealed space rather than smaller space with many leaks as CO will accumulate even in a bit large space provided it's really well sealed.
3. A meter is really handful for knowing how quickly the concentration gets to 1 000 PPM. There's no need to buy expensive meters, just a basic meter will prove handy that measures up to 1 000 PPM.
4. IMO it's better to walk inside the space immediately rather than waiting but try to time the whole stuff when you're really dizzy and want to sleep. That way you won't need sedatives or alcohol and lower concentration of CO in the beginning will put you to sleep quickly.
5. I think it's more peaceful to remain in a low-moderate lethal concentration for 24 hours uninterrupted rather than get knocked down by higher concentration in a couple of minutes. Once you fall asleep, provided the concentration of CO remains at least 800 PPM for a whole day, it will suffocate you in the sleep throughout many hours. It feels very sweet at low concentration, you don't want to leave the space because you're feeling very relaxed and calm. Once you fall asleep, it will be over if nobody escapes you. If the charcoals continue burning and emitting CO for at least 9 hours, it should be enough to never wake up here.
I would do it again but in a larger space like in my room. 2.5 kg of high quality charcoal is enough if the space is thoroughly sealed. Lump charcoal is better since it doesn't contain additives but I'm afraid it won't burn long enough to do its job. IMO a canister full of CO would be great for this purpose since you can set it to release CO at a very slow rate. That way it won't reach lethal levels quickly and will keep accumulating continuously after you fall asleep. Eventually, it will build up to very dangerous levels while you're in a deep sleep and chances of surviving it will be minimized to the lowest.
