Guard against smoke, toxic fumes and moisture with firestop sealants, caulks and putties from Grainger. Intumescent fire seal ensures a tight, dependable seal while fire-resistant putty can help prevent smoke, fumes and moisture from spreading for up to 4 hours. Use mortar for large opening in concrete. it withstands cracking due to temperature fluctuations. Firestop sealants, caulks and putties are suitable for new construction or retrofitting jobs.