A rate-of-rise heat detector will signal an alarm when the temperature in the area rises rapidly, usually about 15 degrees F per minute.

• A. True
• B. False
• C. Depends on model
• D. Only during maintenance

Answer: (A)

Rate-of-rise detectors focus on how fast the temperature changes, not just how hot it gets. If the area’s temperature climbs quickly over a short period, the device trips to warn of a potential fire developing. A common threshold for this rapid rise is about 15°F per minute, meaning an increase of roughly 15 degrees in one minute will trigger the alarm even if the final temperature isn’t extremely high. This makes them effective for catching fast-developing fires while avoiding alarms from slow, gradual heating. Some models may have different or adjustable thresholds, but the described behavior—alarm on a rapid rise near 15°F per minute—is representative of typical rate-of-rise detectors.