This happen a few years ago .The shop I was working in was a old milking barn from the 50's so in the middle was a small catch basin with a 6 inch tile leading outside to a manure holding area . In the back of the shop was our race car area in the front I worked on my farm stuff. One night we were getting the car ready for our next race and one of the guys had to go out back he comes running back in yelling that something had gone up the drain line , So I grabbed a flashlight and checked it out .This huge Possum had made a home in that pipe . I went back in the shop and in the bottom of my tool box I had a box of seal bombs ,So I pulled that grate off the catch basin lit the fuse and tossed it in ! Well as we all know at least we should know ( my excuse was Baileys and coffee ) flamible gas tends to gather in low places well the combo of racing fuel fumes and paint fumes in that tile when the seal bomb went off, the fire that came out looked like a jet engine with full booster, Lucky I did not burn that shop down ! As for the possum he lived for a few days the 22 finally did him in