Fire Detection & Alarm Systems - Disk-shaped Plastic Enclosure 150mm Diameter, Smoke Detection Technology | High Sensitivity, Reliable Performance, Battery Backup

Specifications:

• Detects smoke typically as an indicator
  of fire
• Commercial, industrial, and mass
  residential devices issue a signal to a fire alarm system, while household
  detectors, known as smoke alarms, generally issue a local audible or
  visual alarm from the detector itself
• Smoke detectors are typically housed in
  a disk-shaped plastic enclosure about 150 millimetres (6 in) in diameter
  and 25 millimetres (1 in) thick, but the shape can vary by manufacturer or
  product line
• Most smoke detectors work either by
  optical detection or by physical process, while others use both detection
  methods to increase sensitivity to smoke
• Sensitive alarms can be used to detect,
  and thus deter, smoking in areas where it is banned such as toilets and
  schools
• Smoke detectors in large commercial,
  industrial, and residential buildings are usually powered by a central
  fire alarm system, which is powered by the building power with a battery
  backup