A firestop or fire-stopping is a form of passive fire protection that is used to seal around openings and between joints in a fire-resistance-rated wall or floor assembly. Wikipedia

Fire protection system made of components used to seal openings Wikidata

Any multi-component system designed to stop fire and smoke from migrating through openings around piping, wiring, ductwork, cable trays, bus ducts, etc., as well as through movement joints in walls and floors that are required to have a fire-resistance rating. Wiktionary