Ionized smoke detectors use what material to detect smoke?

Ionized smoke detectors use what material to detect smoke?

• A. Radioactive
• B. Visible light
• C. Air pressure
• D. Magnetic

Answer: (A)

Ionized smoke detectors rely on a small amount of radioactive material to ionize the air inside a sensing chamber, creating a steady electrical current between two plates. When smoke enters the chamber, the smoke particles attach to the ions, reducing the current and triggering the alarm. This method detects flaming fires quickly because many fine particles pass into the chamber early. The other approaches describe different sensing methods not used in ionization detectors: visible light detectors use a light beam and a sensor to detect smoke by scattering or blocking the light; air pressure would rely on pressure changes rather than ionization to sense smoke; magnetic sensors monitor magnetic fields or switches, not smoke particles. The sealed radioactive material is chosen to provide a consistent ionization current, enabling fast response to smoke while remaining safely contained.

Ionized smoke detectors rely on a small amount of radioactive material to ionize the air inside a sensing chamber, creating a steady electrical current between two plates. When smoke enters the chamber, the smoke particles attach to the ions, reducing the current and triggering the alarm. This method detects flaming fires quickly because many fine particles pass into the chamber early. The other approaches describe different sensing methods not used in ionization detectors: visible light detectors use a light beam and a sensor to detect smoke by scattering or blocking the light; air pressure would rely on pressure changes rather than ionization to sense smoke; magnetic sensors monitor magnetic fields or switches, not smoke particles. The sealed radioactive material is chosen to provide a consistent ionization current, enabling fast response to smoke while remaining safely contained.