firethrough

Firethrough is a term used to describe the passage of fire, heat, and smoke through a barrier from one compartment to another, resulting from failure of fire resistance. It implies that a barrier that is meant to separate spaces has been compromised, allowing flames and hot gases to migrate beyond the initial fire location.

It occurs when structural elements, joints, or penetrations compromise compartmentation. Common routes include penetrations for services (pipes, ducts, cables), gaps around doors or frames, unsealed joints in walls or floors, and defects in fire-rated assemblies. The phenomenon can allow flames to propagate rapidly beyond the area initially involved, increasing risk to occupants and complicating firefighting efforts.

Mitigation relies on proper design, installation, and maintenance of fire-resistance rated assemblies. Firestopping and intumescent seals are used to seal penetrations; fire doors and rated wall/floor assemblies are designed to resist flame passage; flashing, dampers, and metal sleeves can reduce leakage. Codes and standards require that penetrations through fire-rated elements be protected to maintain the specified fire-resistance rating.

In fire safety engineering and building assessment, firethrough is evaluated during design-stage calculations and through fire tests of assemblies. Investigations after incidents may cite firethrough as a cause of exposure of adjacent spaces when barriers fail to perform.

Although the term is primarily used in building safety, it also appears in discussions of historical firefighting techniques and in some industry-specific manuals to describe the controlled passage of fire through a barrier in certain processes, though this usage is less common.

See also: fire resistance, compartmentation, firestop, fire door.