Allied Fire Protection Systems, Inc.

Q: How do fire sprinkler systems work?
A: Most sprinkler heads contain a small bulb with a colored liquid inside. This bulb acts as a plug to prevent water from accidentally escaping from the sprinkler. Heat from a fire will cause the liquid to expand, once the pressure gets too high the bulb will burst and the water in the system will be released. The liquid in the sprinkler head comes in a variety of colors, which indicates the temperature required to activate the head:
Orange – 135° F
Red – 155° F
Yellow – 174° F
Green – 200° F
Blue – 286° F
Purple – 360° F
Black – 440° F