Contrary to popular belief, fire sprinklers do not activate in response to smoke. Sprinklers work by being activated to heat. Smoke detectors, which are often installed alongside sprinkler systems, are designed to alert building occupants of a fire. However, sprinklers respond only when the temperature reaches a certain threshold, usually between 135°F and 165°F (57°C to 74°C).
Each sprinkler head is equipped with a heat-sensitive element, either a glass bulb filled with a liquid that expands when heated or a metal fusible link that melts at a specific temperature. When the surrounding air reaches the designated temperature, the element reacts by either shattering the glass bulb or melting the link. This triggers the release of water from the fire sprinkler head, aimed directly at the source of the fire.