I can identify it by the smell. It smells of rotten eggs. All you have to do is look at your wiring anywhere it is accessible. There will be corrosion all over it.
Thanks for that information. I wonder if it smelled that bad when they first put it up? Or did it have to “age” somehow before it began to stink? Smelly Chinese drywall installed by illegals, hired by a contractor who’s long gone “in the wind”! Gosh, how did America fall apart?(sarc)