Detectors used for power shutdown must be located within ____ inches of each sprinkler head.

• A. 12 inches
• B. 18 inches
• C. 30 inches
• D. 24 inches

Answer: (D)

Detectors used for power shutdown are designed to respond immediately when a sprinkler head activates, so they’re placed very close to each head. Positioning the detector within two feet (twenty-four inches) ensures the shutdown signal is triggered быстро and tied directly to the same event that opens the sprinkler. This short distance keeps wiring simple, reduces the chance of signal delay, and minimizes the risk that power remains on long enough to create additional hazards as the fire starts. If the detector were farther away, even a fast-acting sprinkler could be followed by a noticeable delay before power is cut, which undermines the safety goal. The within-twenty-four-inches rule is the standard that makes the shutdown action prompt and reliable.