Firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings. Firestops are designed to restore the fire-resistance ratings of rated wall and/or floor assemblies by impeding the spread of fire through the opening by filling the openings with fire resistant materials.

A common misunderstanding of firestops is that certain materials have certain ratings on their own. For instance, a two-hour rated pipe penetration firestop may consist of a 1/4″ layer of caulking, over top of 2″ of packed rockwool. The layman may assume that the 1/4″ of the caulking provides a two hour fire-resistance rating, generically, regardless of the application, which is incorrect. Materials are not individually rated. Instead, they are used as components within an overall system or certification listing. In addition, all materials in and around the firestop must employ listing and approval use and compliance to conform to the tolerances shown in the certification listing that covers each such installation, including the penetrants, which may have their own product certification requirements apart from forming part of a certification listing for a firestop.