Use to seal and repair boilers, furnaces, flue pipes, stoves, ducts, kilns, chimneys, combustion chambers, and many other furnace and refractory applications. Unique patented clean’n friendly formula meets OSHA’s requirement of less than 0.1% of crystalline silica content. Applies exceptionally smoothly. Can be used on oil, gas, coal, and wood-burning heating systems. Adheres to most building materials. When cured, makes positive non-porous fireproof seal. Will not shrink, crack or crumble. Contains no oils, asbestos, or crystalline silica. 2/5 (1 Review)