Firestop mortars are most typically used to firestop large openings in walls and floors required to have a fire-resistance rating. They are passive fire protection items. Firestop mortars most often exhibit densities near 1 kg/L. This makes the product easy enough to handle, yet heavy enough to absorb a lot of heat from penetrants, to keep the unexposed side of the assembly cool.
Firestop mortars differ in formula and properties from most other cementitious substances and cannot be substituted with generic mortars without violating the listing and approval use and compliance.