Sprinkler systems control fire by cooling the heat load and the air surrounding the fire. These fire-safety devices are usually installed on ceilings and upon fire detection they will release a water spray which extinguishes or controls the fire.
Sprinklers use a device which activates them when the temperature reaches a certain threshold. This device can be either a fusible substance that will melt at a certain temperature, or a glass bulb that contains liquid that will burst the bulb when heated. This allows a water pressure to be released from a plug and causes water to flow out through the sprinkler.
Sprinkler systems can be designed to activate individual sprinkler heads so that the water spray is only released where required, minimising water damage.