Automatic Fire Sprinklers & their Operating Temperatures

Did you know that some automatic fire sprinklers utilize frangible bulbs that follow a standardized color-coding convention indicating their operating temperature? The table below is a simplified table from NFPA 13 that shows the temperature classification which corresponds to the temperature rating of the sprinkler. Some automatic sprinklers use a fusible link that activates at a predetermined temperature. The fusible link either melts or has a frangible liquid-containing glass bulb that breaks, causing the water pressure to push a plug out of the sprinkler orifice, resulting in water releasing from the sprinkler.

As a safety professional, it is important to be aware of sprinkler’s temperature range, their classification, and their color bulb to ensure that an area has the correct sprinkler type. Automatic fire sprinklers are extremely important in preventing widespread damage from fires and if an area has been classified incorrectly, it could be devastating for the area that the sprinkler is supposed to be protecting.

For example, if an area is classified as “Ordinary”, it’s fire sprinkler should operate in the temperature range of 135° - 170° F, the fusible link will be uncolored or black, and the frangible bulb color will be Orange or Red.