What function does a beam detector serve in fire detection?

A beam detector serves the function of projecting a beam of light, typically in the infrared or visible spectrum, across a space. When smoke particles enter the path of this light beam, they scatter and interfere with the light. This interruption triggers the alarm system, indicating the presence of smoke, which is often an early sign of fire. This method is particularly effective in large areas such as warehouses, auditoriums, and atriums where conventional detectors might be less effective due to distance or environmental factors.

In contrast, the other functions described in the options include methods of detection that do not align with the operational mechanics of a beam detector. Temperature change measurement is characteristic of heat detectors, while sound emission pertains to alarm systems rather than detection mechanisms. Chemical reactions are involved in certain types of flame detectors but not in beam detectors. Thus, the unique operational principle of the beam detector—utilizing light projection and smoke interruption—clearly defines its role in fire detection systems.