It's quite nasty if you don't finish the job. You can have flu-like symptoms for up to a month if you get a mild case, or worse you can end up with a month of n

It's quite nasty if you don't finish the job. You can have flu-like symptoms for up to a month if you get a mild case, or worse you can end up with a month of nausea and vomiting. If you're going this route, go for bottle carbon monoxide. A CO concentration over 1% can kill in 2-3 breaths (IE before you have nausea, vomiting and convulsions) so I imagine breathing 100% CO could do the job in a single breath. It'd be as simple as inflating a balloon and inhaling. The idea here would be to get the concentration percentage as high as fast as possible.