Heat detectors are devices designed to sense changes in temperature, typically used in fire alarm systems. They work by detecting heat from a fire, triggering an alarm when the temperature exceeds a certain threshold. There are two main types: fixed temperature detectors, which activate at a specific temperature, and rate-of-rise detectors, which respond to rapid increases in temperature. These detectors are commonly installed in buildings, warehouses, and other areas where smoke detectors may not be suitable. They are particularly effective in environments with dust, steam, or other airborne particles that could interfere with smoke detection.