Firestop gap sealant is an environmentally friendly one-component firestop material that quickly and effectively seals hard-to-reach gaps. It is suitable for joint sealing between curtain walls and floor edges, as well as for gaps with high elongation. It offers excellent airtightness and watertightness, with superior elastic deformation capability. It does not crack upon use and expands when heated during a fire, rapidly sealing the voids left by the combustion of flammable materials. This prevents the spread of fire and smoke through the facade, reducing the extent of fire damage.