A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding, which is based on elaborate fire testing as well as environmental testing, in some cases.

Unprotected or unbounded openings in fire separations void the fire-resistance ratings of the fire separations that contain them and thus, both in practical and legal terms, collapse the fire compartments of which these fire separations form a part, which affects the fire safety plan of the entire building. Firestops are specifically designed to restore the fire-resistance ratings of rated wall and/or floor assemblies by bounding the openings through approved firestops.