What device activates when heat creates a change in temperature at the detector?

The device that activates when heat creates a change in temperature at the detector is a heat detector. Heat detectors are specifically designed to respond to changes in temperature, which occur when there is a fire. These devices monitor the surrounding environment for significant increases in temperature, which can indicate the presence of a fire.

In a situation where a fire occurs, the rising temperature causes the heat detector to trigger an alarm, alerting occupants to the potential danger. This property of heat detectors makes them particularly effective in areas where smoke detectors might not be suitable, such as kitchens or garages, where cooking activities or other heat sources could cause false alarms.

While smoke detectors are designed to react to particulate matter in the air, such as smoke produced from combustion, and gas detectors sense specific combustion gases, these devices operate on different principles than heat detectors. Therefore, the unique function of heat detectors in responding to temperature changes makes them the correct choice in this context.