Certified Facility Manager (CFM) Practice Exam

Alarm-sounding devices that activate when smoke particles obscure light are known as what?

1. Ionic smoke detectors

2. Photoelectric smoke detectors

3. Thermal detectors

4. Optical detectors

The correct answer is: Photoelectric smoke detectors

The correct choice refers to photoelectric smoke detectors, which are designed to detect smoke particles in the air by utilizing a light source and a light-sensitive sensor. In this type of smoke detector, a beam of light is emitted and, when smoke particles enter the sensing chamber, they scatter the light. This scattering triggers the alarm. This mechanism makes photoelectric smoke detectors particularly effective at sensing smoldering fires, which produce larger smoke particles. Other options include ionic smoke detectors, which operate differently by using a small amount of radioactive material to ionize the air and detect smoke via changes in the ionization level. Thermal detectors respond to changes in temperature rather than the presence of smoke particles, making them less effective for early detection of smoke from smoldering fires. Optical detectors generally refer to devices that observe light but may not be specifically tailored for smoke detection in the way photoelectric detectors are.