Sometimes guests can really surprise you with what they will do. The first guest I let self-check-in (because they were arriving at 1:30 am), looked at the already-built fire in the fireplace and decided it would be romantic to have a fire. So they lit the fire. At 2 am I heard beep, beep, beep . . . beep, beep, beep. The only noise I can hear from the downstairs unit in my duplex is the smoke detector. When I opened my back door to go down and inspect, the outside back door was open and there was smoke pouring out the back door. I went down to see what had happened and found the young woman pouring a glass of water on the still-smoldering fire while the young man ran around trying to open the windows (this was February in Minnesota–storm windows on every window). Smoke was all over the place and filled the tops of the rooms down to about chin level. It seems they were from Florida and did not know about opening the flue. Obviously my fault for pre-building the fire.
My house rules at the time said I was to be present for the first fire (so I could do some educating). They were young and didn’t read them. Since they were here for the Super Bowl, there were no other places for them to go so they finished their stay, to my great financial advantage. They did do a lot of work cleaning the place up. After that I did not pre-build the fire and I put a tent card on the mantle saying to contact me before having a fire (in case they bought a log from Super America).