Fire sprinkler heads deliver a high-pressure flow of water or dry chemicals to a fire. They are usually heat-activated and part of a larger fire prevention and safety system. Most fire sprinkler heads attach to a network of pipes that terminate at a pressure regulator, which controls distribution from the fire suppression reservoir. This reservoir contains water or some other fire suppression agent such as carbon dioxide (CO2), argon (Ar), or high-expansion foam. The heat-activation features of fire sprinkler heads are implemented through the use of heat-sensitive seals. These seals are used with thin, liquid-filled tubules that are designed to burst and permit the discharge of the fire suppressant at a specific temperature. Typically, these tubules are color-coded to indicate the maximum allowable temperature.