Last night, as I was doing some electrical work, I decided I needed to open a wall up. So I pulled out my utility knife and started cutting out a section; to my surprise, it wasn't drywall (or plaster), but rather some sort of cardboard-like substance. It's about as thick as normal drywall, held up by drywall nails. What is this, and how long ago were people using it? Are there any potential health hazards I should be aware of when working on/around it?
- posted
19 years ago