W
Whyme
mdf fibres, celotex when sawn, fibres from inset fire coals. The list goes on if its fire proof or insulating its gonna cause damage....dont know if your all aware but old vermiculite insulation '1980's could be contaminated with asbestos because of where it was mined. Theres loads of 80s lofts full of that ( nightmare if you drop a spanner)..