Asbestos-containing material (ACM)

The 1 percent line matters because it is the legal trigger. Federal rules treat a material as ACM when a lab finds more than 1 percent asbestos in it. Under that line, the same rules generally do not call it ACM.

You cannot see the percentage with your eyes. Two tiles that look the same can test differently. That is why a certified inspector takes samples and a lab reads them under a microscope.

Knowing a material is ACM changes your next step. It decides whether you can renovate on your own schedule or need a plan, notices and trained crews. The EPA says exposure happens when material is disturbed or damaged enough to release fibers, so ACM that stays intact is a smaller worry than ACM that you plan to cut.

Ask for the lab report before any work starts. If a material is ACM and falls into a regulated class, see RACM. If it is hard and bound, see non-friable asbestos.