Sprinkler systems are intended to either "control" the fire or to "suppress" the fire. "Control mode" sprinklers are intended to control the heat release rate of the fire to prevent building structure collapse, and pre-wet the surrounding combustibles to prevent fire spread. The fire is not extinguished until the burning combustibles are exhausted or manual extinguishment is effected by firefighters. "Suppression mode" sprinklers (formerly known as "Early Suppression Fast Response" (ESFR) sprinklers) are intended to result in a severe sudden reduction of the heat release rate of the fire, followed quickly by complete extinguishment, prior to manual intervention.