1390035 FLAMESEAL CAULK OSI 10.5oz | OSI FlameSeal fire, smoke and draft stop sealant is a non-flammable, latex-based fire stopping sealant. This one component sealant is designed for use in both residential and commercial fire stopping applications. Developed to seal service penetrations and joints in fire separations and firewalls, it prevents the passage of flame, smoke and fumes under actual fire conditions of 1 hr, 2 hr and 3 hr fire resistance rated systems. It improves STC values and upgrades sound quality. OSI FlameSeal utilizes a special waterborne technology that is both non-flammable and non-hazardous and cleans up easily with water. Cured product is also mold-and mildew-resistant.