The DiversiTech® 800-009 water-based fiber-reinforced duct sealant is formulated for indoor or outdoor use. Meets U.L. Class 1 rating and local codes while featuring long term flexibility and strength. It can be used on metal heating, ventilating, and A/C duct systems as well as fiberglass duct board systems and flex duct systems. Recommended for use to 10 in. of water column pressure without the need for fiberglass mesh reinforcement. Diversitech Pro-Air Duct Sealant, Pail, 1 gal, White, <37 % VOC