Which smoke alarm is activated by visible combustion products?

• A. Ionization
• B. Carbon Monoxide detector
• C. Photoelectric
• D. Heat

Answer: (C)

Smoke alarms respond to different smoke characteristics, so some are better for visible smoke from smoldering fires. The detector that is activated by visible combustion products is the photoelectric type. It uses a light beam inside a chamber; when smoke enters, the particles scatter the light toward a sensor, triggering the alarm. This makes it particularly sensitive to the larger particles found in smoldering, visibly smoke-filled conditions. Ionization detectors rely on ionized air and respond faster to the tiny particles produced by flaming fires, not as quickly to visible smoke. Carbon monoxide detectors detect CO gas, not smoke, and heat detectors respond to high temperatures rather than smoke. So the device activated by visible combustion products is the photoelectric detector.