Different, and perhaps not as discussed

[scream-in-the-pillo]

I have been digging around and it seems like using pharmacy chems is not the cheapest option. However, during my digging I found a bit about CO. If you are in an enclosed space with a bunch of lit candles it can reach fairly high levels of CO that could do the trick. If candles are not your style, perhaps getting hands on some HCOOH a H2SO4 mixed in proper ratio will give you the same result. Several hundred ppm should get you there but I have not looked more into it. But it is an alternative. Do you have any other unusual methods not discussed?