Duct Smoke Detector Make Up Air Unit

Duct detectors aren t a replacement for room sensors.

Duct smoke detector make up air unit.

The detector shall be listed for the air velocity temperature and humidity anticipated at the point where it is installed. Therefore duct smoke detectors are typically considered mechanical equipment devices instead of life safety devices. Duct smoke detection may be useful in preventing injury and property dam age in instances such as the following. Duct detectors smoke detection nfpa 90a code requirements.

A heating ventilating or air conditioning hvac fan motor overheats and resulting smoke is sensed by the duct smoke detector installed in the main supply duct. Duct smoke detector are important part of a fire protection syste. It is preferred that the occupied and non occupied areas and spaces have smoke detectors simply because the fans in air handlers or that move air through duct work may not be operational at all times so having smoke detectors in the duct work will not offer the amount of protection that smoke detectors would offer in the spaces or area served whether those areas or spaces are occupied or not. Where a smoke damper is installed within a duct a smoke detector shall be installed in the duct within 5 feet 1524 mm of the damper with no air outlets or inlets between the detector and the damper.

The imc commentary provides further explanation on the intent of the code. The duct smoke detector is equipped with an auxiliary relay. Ahu smoke detector must shutdown upon alarm. If the duct system is designed to carry more than 2000 cfm 5 tons nominal of air you need one in the return if imc is being followed and the supply if nfpa is being followed.

Testing air handling unit duct smoke detector. Where to place smoke detectors in the ductwork on commercial projects to comply with code. Nfpa 72 also states that a duct smoke detector is not allowed to replace an area smoke detector mainly because if the air handling unit ahu is not running the detector would not detect smoke.