Mike Lamb 14 Report post Posted March 5 (edited) I ran into this Pyrobar stuff the other day. It was lining the floor beneath a back porch. I did some research and it was a fire proof insulator used around structural members but also used to build non-bearing walls. The mortar used for this product probably contains asbestos and workers often cut it with a saw. Here are some links if anyone is interested: https://archive.org/details/PyrobarGypsumTile Edited March 5 by Mike Lamb Share this post Link to post Share on other sites
Bill Kibbel 39 Report post Posted March 5 I've come across it a few times. Boiler room ceilings, stair and elevator towers. Tests showed it contains a very small percentage of fibers, surprisingly from wood. Share this post Link to post Share on other sites
