UL Classified Intumescent Firestop Sealant is a fire rated, general purpose sealant for use on through-penetrations and construction joints. It is a single component, non-sag, water based sealant and smoke seal that is easy to apply and clean up. BOSS® 816+ will prevent the spread of toxic gases, water, smoke and fire through joint openings and through penetrations. BOSS® 816+ is suitable for adhesion to almost any surface and remains flexible, making it ideal for both horizontal and vertical joints, subject to vibration or dynamic movement. It bonds quickly, has excellent adhesion and is non-toxic.