kiinteälämpöilmaisimet

Kiinteälämpöilmaisimet, known in English as fixed temperature heat detectors, are a type of fire alarm device that responds to a specific, predetermined temperature threshold. Unlike rate-of-rise heat detectors, which activate when the temperature increases rapidly, fixed temperature detectors trigger only when the ambient temperature reaches a fixed point. This makes them suitable for environments where a steady rise in temperature is common but not indicative of a fire, such as kitchens or industrial areas with heat-producing machinery.

These detectors typically consist of a bimetallic strip or a thermistor. In bimetallic strip detectors, two different metals with varying thermal expansion rates are bonded together. When the temperature rises to the activation point, the differential expansion causes the strip to bend, closing an electrical circuit and triggering the alarm. Thermistor-based detectors use a semiconductor whose resistance changes significantly with temperature. When the resistance reaches a certain value corresponding to the set temperature, the alarm is activated.

The activation temperature for fixed heat detectors is usually stated in degrees Celsius. Common activation points include 57°C (135°F) and 77°C (170°F), with higher temperatures available for specialized applications. It is important to select the appropriate activation temperature to ensure timely detection of a fire while minimizing false alarms caused by normal operating temperatures. Fixed temperature heat detectors are generally less sensitive to rapid temperature fluctuations but provide reliable detection in environments where smoke detectors might be prone to false alarms due to steam, dust, or fumes.