2026 Complete Practice Test for Plans Examiner in Fire and Emergency Services

Smoke detectors rely on two main sensing methods: ionization and photoelectric detection. Photoelectric detectors sense smoke when particles scatter or obstruct a light beam, which can be described as light scattering or light obscuration. Because of that, the types of smoke detectors include ionization and photoelectric (with the photoelectric method described by these terms). The other listed devices—heat detectors, flame detectors, and carbon monoxide detectors—are not smoke detectors. Some detectors combine both ionization and photoelectric sensing in one unit, but the essential concepts are ionization and photoelectric (including light scattering and light obscuration).