Which type of fire detection system operates on the principle of rate of temperature rise?

Which type of fire detection system operates on the principle of rate of temperature rise?

• A. The thermocouple system
• B. The thermoswitch system
• C. The thermistor-type continuous-loop system
• D. The pneumatic-type continuous-loop system

Answer: (D)

Rate-of-rise detection looks for how quickly the temperature climbs, not just how hot it ends up. In a pneumatic continuous-loop fire detector, the loop is filled with air at a controlled pressure. When a fire heats the surrounding area, the air inside the loop heats and expands, raising the pressure. The detector monitors how fast that pressure increases; a rapid temperature rise causes a rapid pressure rise, which triggers the alarm. Other detectors rely on absolute temperature or resistance changes at sensor locations rather than the rate of temperature change. A thermocouple responds when a certain temperature is reached. A thermoswitch also actuates at a fixed temperature. The thermistor-type continuous-loop changes resistance with temperature along the loop, signaling when a particular temperature is reached, not the rate of rise. So, the pneumatic continuous-loop system operates on the principle of rate of temperature rise.

Rate-of-rise detection looks for how quickly the temperature climbs, not just how hot it ends up. In a pneumatic continuous-loop fire detector, the loop is filled with air at a controlled pressure. When a fire heats the surrounding area, the air inside the loop heats and expands, raising the pressure. The detector monitors how fast that pressure increases; a rapid temperature rise causes a rapid pressure rise, which triggers the alarm.

Other detectors rely on absolute temperature or resistance changes at sensor locations rather than the rate of temperature change. A thermocouple responds when a certain temperature is reached. A thermoswitch also actuates at a fixed temperature. The thermistor-type continuous-loop changes resistance with temperature along the loop, signaling when a particular temperature is reached, not the rate of rise.

So, the pneumatic continuous-loop system operates on the principle of rate of temperature rise.