Sprinkler heads used in computer rooms activate at what temperature?

Sprinkler heads are activated by heat, which causes a fusible link to melt or a liquid-filled glass bulb to shatter, releasing the water. According to NFPA 13, sprinkler heads have different temperature ratings for various environments. The "Ordinary" temperature classification, commonly used in areas like computer rooms, ranges from 135°F to 170°F (57°C to 77°C). The lowest standard activation temperature in this common classification is 57°C (135°F). This temperature is high enough to prevent accidental discharge from the heat generated by IT equipment but low enough to activate in the early stages of a fire.

B. 27°C (81°F) is within the recommended ASHRAE operating range for a data center and would cause constant, unwanted sprinkler activation.
C. 70°C (158°F) is also a valid "Ordinary" rating, but 57°C (135°F) is the lowest and a very common standard temperature for this classification.
D. Sprinkler heads are activated by a specific ambient temperature reaching the head, not by direct contact with a flame.

1. National Fire Protection Association. (2019). NFPA 13: Standard for the Installation of Sprinkler Systems. (Chapter 7, Section 7.2.4.1, Table 7.2.4.1 "Temperature Ratings, Classifications, and Color Codings," lists the "Ordinary" temperature classification as 135–170°F / 57–77°C).

2. National Fire Protection Association. (2021). NFPA 75: Standard for the Fire Protection of Information Technology Equipment. (Chapter 8, Section 8.2.1, refers to NFPA 13 for the installation of automatic sprinkler systems, thus incorporating its temperature rating standards).