GBs Fire-Gard Fire stopping Caulk Sealant is a high performance fire barrier for use on ceilings, floors and walls. The caulk effectively fills and seals the space around wires, vents, pipes, ducts, and other mechanical penetrating items to help control the spread of flames, smoke and toxic gases. Tested to provide up to a 4 hour F-rating in through-penetrations, the sealant is ideal for electrical, plumbing, HVAC and head-of-wall system applications.