Fire and smoke hazard
I recently inspected this home built in the early 1970’s. The ceiling was a textured type and it looked like the older Celotex type covering. It felt more like Styrofoam. So, I found a loose piece of about 2″ square and brought it home to do some research. I got out a lighter and held it onto the piece for seconds – it didn’t stop burning and smoking for over a minute!