Certified Fire Protection Specialist (CFPS)

Air sampling-type smoke detection systems use which detection principle?

1. Ionization

2. Photoelectric light-scattering

3. Thermal detection

4. Humidity sensing

The correct answer is: Photoelectric light-scattering

Air sampling-type smoke detection systems primarily operate on the photoelectric light-scattering principle. This method involves drawing air into a detection chamber through a network of sampling tubes. Once the air enters the chamber, any smoke particles that are present cause light to scatter. A photoelectric sensor detects this scattered light and triggers an alarm when the levels of scattering indicate the presence of smoke. This method is particularly effective in detecting various types of smoke, including those from slow smoldering fires, which can generate more smoke and particulate matter. The ability to sample air continuously makes these systems highly sensitive, capable of detecting smoke before it becomes visible or reaches a higher concentration, thus enhancing fire safety. Other methods like ionization or thermal detection represent different principles. Ionization detectors utilize a small amount of radioactive material to produce ions in the air, while thermal detectors activate based on temperature changes rather than smoke particles. Humidity sensing does not relate to smoke detection at all, making it an unsuitable principle for identifying smoke. Understanding these principles helps in selecting the right detection system for specific environments and fire risks.