Abstract: A heat activated sealing apparatus for closing and locking a plurality of ventilation damper blades of a ventilation framework includes a fire detection assembly for detecting a fire condition and an actuator. A damper closure assembly includes an axle in communication with the actuator of the fire detection assembly and operatively coupled to the plurality of dampers of the ventilation framework, the axle being selectively rotatable between a start configuration at which the plurality of ventilation dampers are at the open configuration and a deployed configuration at which the plurality of ventilation dampers are at the closed configuration. The damper closure assembly includes a locking assembly movable between an unlocked configuration allowing rotatable movement of the axle and a locked configuration not allowing rotatable movement of the axle. The locking assembly is movable to the locked configuration only when exposed to a predetermined amount of heat from the fire condition.