Not a type of smoke detector, which option is incorrect?

• A. Ionization
• B. Light scattering
• C. Photoelectric
• D. Heat detector

Answer: (D)

Smoke detectors rely on sensing methods that respond to smoke particles. Ionization detectors use a small radioactive source to ionize air; when smoke enters the chamber, the ion flow is interrupted and the alarm is triggered quickly, especially for flaming fires. Light scattering, or optical detectors, shine light into a chamber and rely on smoke particles scattering that light toward a sensor, which detects the presence of smoke, often catching smoldering fires. Photoelectric detectors are a type of optical detector that use this light-scatter principle.

Heat detectors, by contrast, are designed to sense heat or rapid temperature rise, not smoke particles. They respond to heat conditions rather than smoke in the air, so they are not considered smoke detectors.