No Visible Signs
I was in my parent’s house and thought I smelled chlorine. I also heard a low buzzing and the hall lights were brighter than usual. I felt silly because there was no smoke or visible signs, but I told my parents I thought we had an electrical fire, and they called 911.
Turns out, we did indeed have an electrical fire, which caused the smell of chlorine to proliferate as the wires were burning.
Story credit: Reddit / duckingcluttered