BEAM DETECTORS

  • Beam smoke detection provides better coverage than spot detection for high-ceiling and open-area applications, such as warehouses, atriums, and barns. Depending upon the application,
  • beam smoke detection can be the more economical choice, often requiring only one detector to cover large areas that would require multiple spot detectors.
  • Reflected beam smoke detectors respond well to all types of fires and work with all colors of smoke.
  • Reflected beam smoke detectors also provide mounting options that help minimize smoke stratification concerns. See NFPA 92B: Standard for Smoke Management Systems in Malls, Atria, and Large Spaces, for more detailed information.

Beam detectors provide a cost effective method of covering wide open plan areas such as galleries and atria, however care should be taken that activities in the space do not obstruct the beam and that the building structure is such that the beam does not ‘move’ or false operation may result. This detector consists of two components, a light transmitter and a receiver, that are mounted at some distance (up to 300 ft/100m) apart. As smoke migrates between the two components, the transmitted light beam becomes obstructed and the receiver is no longer able to see the full beam intensity. This is interpreted as a smoke condition, and the alarm activation signal is transmitted to the fire alarm panel.

If optical beam detectors are mounted within 2feet/ 600mm of the ceiling level, they should be positioned such that no point in a protected space is more than 25 ft / 7.6m from the nearest part of the optical beam. Should the beam detector be mounted more than 600mm below ceiling level then spacing should be altered to 12.5% of the height of the beam detector above the highest likely seat of any fire. Other than the part of the beam within 500mm of the beam’s transmitter or receiver, if any other section of a beam which runs closer than 500mm to any wall partition or other obstruction to the flow of hot gasses, that section of the beam should be discounted from providing protection.

BEAM VS. SPOT-TYPE DETECTORS
  • theoretical maximum area coverage for projected beam detector (19,800 sq. ft.) compared to one spot-type detector ( 900 sq ft.)
  • beam detection offers 20 times the coverage of a single spot-type smoke detector!

Economics of Beam Smoke Detection: Spot Detector vs. Reflected Beam Smoke Detector

  • Spot Detector:
    • Purchase 22 spot detectors x S 30.00 = $660 (approx. retail cost)
    • Install 22 spot detectors x 1 hour each = 22 hours
    • Maintenance and testing per NFPA 72 = 15-30 minutes per detector = 16 hours
  • Reflected Beam Smoke Detector:
    • Purchase 1 reflected beam smoke detector = $550 (approx. retail cost)
    • Install 1 reflected beam smoke detector = 2 hours
    • Maintenance and testing per NFPA 72 = 15 minutes