Red Devil F-Seal 181 is a premium fiber-reinforced water-based duct sealant engineered for superior performance in all HVAC systems. This versatile sealant is UL 181 A-M & B-M certified, making it suitable for metal, fiberglass, and flexible ducts. Its fast-drying, low VOC formula ensures quick application and safety in sensitive environments. F-Seal 181 exceeds all SMACNA Pressure and Sealing Classes, providing unmatched sealing capabilities for high, medium, and low-pressure HVAC systems. The durable, weather-resistant formula is perfect for both indoor and outdoor use, resisting mold, mildew, and UV damage. It contributes to LEED EQ Credit 4.1 and meets CA Dept. of Public Health Emission Requirements V1.1, 2011. This USA-made product offers excellent adhesion, flexibility, and can be painted after full cure. For best results, apply in temperatures between 40°F and 110°F, allowing 24-72 hours drying time before pressure testing. F-Seal 181 is your go-to solution for efficient, long-lasting HVAC duct sealing.