Duct Smoke Detector: Air Sample Tube


Duct Smoke Detectors are a key component of Fire Detection and Fire Alarm systems. The duct smoke detector samples air for early detection of smoke and products of combustion present in air moving through HVAC ducts. The Duct Smoke Detector should be compatible with Building Automation and Fire Alarm systems. Duct Smoke Detectors use Ionization or Photoelectric sensing technology.

Ionization Duct Smoke Detectors react to changes in ionized particles. Ionization technology is generally more sensitive than Photoelectric at detecting small particles which tend to be produced by flaming fires. These fires spread and consume combustible materials rapidly. Photoelectric Duct Smoke Detectors react to how smoke affects light and are generally more sensitive than Ionization at detecting large particles. These particles are produced in greater amounts by smoldering fires, which may smolder for hours before bursting into flames.

Duct Smoke Detectors continuously sample the air with 2 tubes extending into the HVAC duct. Air flowing through the duct is forced into holes in the intake tube then passing over the detector head. The sampled air is then forced back out the exhaust tube into the duct. When the smoke particles in the air stream reach the detector head alarm threshold - the duct smoke detector will go into alarm mode.