Rate of Rise detectors depend on expansion characteristics of heat and activate at a rise rate of 12 to 15 degrees per minute. Which option best captures this?

• A. Expansion characteristics of heat; will activate if there is a 20 degree per minute rise.
• B. Ambient humidity levels.
• C. Expansion characteristics of heat; will activate if there is a 12-15 degree per minute rise.
• D. Air flow rate.

Answer: (C)

Rate-of-rise detectors trigger based on how fast heat increases, not on a single high temperature. They use a heat-sensitive element whose expansion responds to the rate of temperature change. When the temperature climbs about 12 to 15 degrees per minute, the element expands enough to set off the alarm. This captures the mechanism (expansion characteristics of heat) and the operating threshold (12–15 degrees per minute). Humidity and air flow aren’t the defining factors for this type, and a faster rise like 20 degrees per minute is outside its specified range.