Which type of smoke detector detects particles and aerosols produced during combustion that are too small to be seen by the naked eye?

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Multiple Choice

Which type of smoke detector detects particles and aerosols produced during combustion that are too small to be seen by the naked eye?

Detectors that sense extremely small particles produced by combustion rely on ionization of the air. In an ionization detector, a small amount of radioactive material ionizes the air in a chamber, creating a steady current. When very fine smoke particles or aerosols enter that chamber, they capture ions and disrupt the current, triggering the alarm quickly. These tiny particles are characteristic of many flaming fires and are often not visible to the naked eye, which is why this type is best for detecting them. In contrast, other detectors focus on different signals. A photoelectric detector uses light scattering: smoke particles scatter light into a sensor and are typically more responsive to larger smoke particles from smoldering fires. Heat-based detectors—rate-of-rise and fixed-temperature—rely on temperature changes rather than smoke, so they aren’t about detecting the presence of small smoke particles at all.

Detectors that sense extremely small particles produced by combustion rely on ionization of the air. In an ionization detector, a small amount of radioactive material ionizes the air in a chamber, creating a steady current. When very fine smoke particles or aerosols enter that chamber, they capture ions and disrupt the current, triggering the alarm quickly. These tiny particles are characteristic of many flaming fires and are often not visible to the naked eye, which is why this type is best for detecting them.

In contrast, other detectors focus on different signals. A photoelectric detector uses light scattering: smoke particles scatter light into a sensor and are typically more responsive to larger smoke particles from smoldering fires. Heat-based detectors—rate-of-rise and fixed-temperature—rely on temperature changes rather than smoke, so they aren’t about detecting the presence of small smoke particles at all.

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