Which heat detector activates when the temperature increases more than a set amount in a given time?

Which heat detector activates when the temperature increases more than a set amount in a given time?

• A. Open-chamber heat detector
• B. Rate-of-rise heat detector
• C. Closed-chamber heat detector
• D. Variable-threshold heat detector

Answer: (B)

Heat detectors respond in two main ways: some trigger when the temperature reaches a fixed high value, while others trigger based on how quickly the temperature rises. The description in the question matches rate-of-rise detectors, which activate when the temperature increases by a certain amount over a short period. This means they respond to rapid heating from a developing fire, even if the absolute temperature isn’t extremely high yet. Fixed-temperature detectors (such as open-chamber and closed-chamber types) go off when the ambient temperature hits a preset threshold, regardless of how fast the temperature is changing. Variable-threshold detectors adjust to ambient conditions to reduce nuisance alarms but still rely on reaching a high temperature, not the rate of change.

Heat detectors respond in two main ways: some trigger when the temperature reaches a fixed high value, while others trigger based on how quickly the temperature rises. The description in the question matches rate-of-rise detectors, which activate when the temperature increases by a certain amount over a short period. This means they respond to rapid heating from a developing fire, even if the absolute temperature isn’t extremely high yet.

Fixed-temperature detectors (such as open-chamber and closed-chamber types) go off when the ambient temperature hits a preset threshold, regardless of how fast the temperature is changing. Variable-threshold detectors adjust to ambient conditions to reduce nuisance alarms but still rely on reaching a high temperature, not the rate of change.