Certified Fire Protection Specialist (CFPS) Practice

Gas-sensing fire detectors operate based on specific principles that enable them to detect the presence of gases associated with combustion. The primary operating principles include the optical, thermal, and chemical principles.

The optical principle involves detecting changes in light caused by smoke or combustion gases, commonly used in photoelectric smoke detectors. The thermal principle operates by sensing changes in temperature or heat associated with a fire. The chemical principle detects specific gases produced during a fire, like carbon monoxide, by using sensors that respond to changes in chemical composition.

The pneumatic principle, however, is not associated with gas-sensing fire detection. It generally refers to systems that operate through the movement of air or gas under pressure. This principle is not utilized in gas-sensing fire detectors, making it the correct answer to the question. Understanding these principles helps in designing effective fire detection systems that are sensitive to the specific conditions indicative of a fire.