OSI Fire Block Foam is a single component, low-pressure minimal expanding polyurethane foam packaged in a pressurized metal container. Product is designed specifically for use Type VA, occupancy group R3 and R5 (wood frame) buildings, to seal openings in concealed spaces to resist the migration of fire and hot gases. The Fire Block foam cures upon reaction with moisture to form a flexible, urethane foam that is effective against the passage of smoke and toxic gases through service penetrations. Foam adheres to most types of building materials including wood, concrete, brick, metals, cable jacketing; and will not harm PVC, CPVC and PEX pipe/tubing. It complies with all Federal and State VOC regulations.