i'm an asbestos worker and have been for 20 years. like steve said, the rule of thumb is if your not sure and do not test ,assume it is asbestos. we treat anything built before 1980 as asbestos, this would include floor tile (9x9 squares), window caulk and alot of other building materials. they only way it is dangerous is if it becomes friable (airborne).dust mask are not approved for asbestos dust . if you would like anymore info ,please contact me.