I wanted to try a pot/stove combination and fired up a pop-can stove on my range top. I had a small circle of aluminum with the edges rolled up that I put under the stove to use for a priming pan. I filled the stove and lit it and it warmed up normally. I went ahead and tried the pot I had in mind and the stove was still burning when I took the pot off. I had the whole works in a large pyrex pan. I put another small pot over the stove to snuff the flame and that wasn't a good idea-- there was enough air in there so the stove just overheated and I got a big flare when I took the small pot off to see if it was still burning. It singed the hair on my arm and made me jump, but I thought that was the end of it.
What I didn't notice is when the stove flared up, it blew the remnants of the match I used to light it across the room to a little office area we have in the kichen and the re-ignited match landed on some papers. I went out of the kitchen for a moment and came pack to dump out the hot water and clean up from my trial. I saw smoke in the kitchen, but no flames or source for the smoke. When I turned around and looked in the office alcove, I was greeted with a small stack of papers with flames rising from one edge.
I was able to snuff out the flames with a wet dish towel, but I got the scare of my life. If I hadn't come back into the kitchen right away, the flames would have quickly reached more papers on a shelf above and it would have been WAY too exciting.
So, do your experimenting outside and never try to cover a burning alcohol stove with another container-- douse it with water or just let it burn out.