Photoelectric sensors function by detecting ultraviolet or infrared light reflected off smoke particles, whereas ionization sensors rely on a small internal electric current that is interrupted when smoke enters the chamber. Typically, ionization alarms are more responsive to fast-moving, flaming fires, while photoelectric models are superior at identifying slow-burning, smoldering fires. Despite these technical differences, both types offer comparable accuracy across various fire scenarios; ultimately, ensuring the units are properly placed throughout a building is the most critical factor for safety.
The information for this answer was found on our Carbon Monoxide & Smoke Detector Laws answers.