Final answer:
Rate of Rise heat detectors are triggered when the temperature increases at a rate of 15°F per minute.
Step-by-step explanation:
Rate of Rise heat detectors are designed to trigger an alarm when the rate of temperature increase exceeds a certain threshold. They are a type of fire alarm detector that responds to rapid changes in temperature, typically due to fire. The standard rate of temperature rise that would activate a Rate of Rise heat detector is 15°F per minute. So, answering the question, Rate of Rise heat detectors operate when the temperature increases 15°F per minute.