Mike Lamb 25 Report post Posted March 5, 2018 (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, 2018 by Mike Lamb Share this post Link to post Share on other sites
Bill Kibbel 43 Report post Posted March 5, 2018 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
