Which sprinkler color uses a Blue bulb?

• A. Blue
• B. Green
• C. Red
• D. White

Answer: (A)

Sprinkler heads use a glass bulb filled with liquid that expands when heated. When the heat reaches the bulb’s rated temperature, the bulb breaks and the sprinkler releases water. The color of the bulb shows the activation temperature category for that head. A blue bulb indicates a head with a higher heat rating, so recognizing blue tells you you’re dealing with the blue-coded, higher-temperature head. Other colors correspond to different ratings, but the blue color itself is the cue for that higher activation temperature.