Duct Smoke Detector Make Up Air Unit

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.

Duct smoke detector make up air unit. 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. 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. Duct detectors smoke detection nfpa 90a code requirements.

The imc commentary provides further explanation on the intent of the code. A duct smoke detector should shut off a typical blower and fresh air and turn on the exhaust. 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. Duct smoke detection may be useful in preventing injury and property dam age in instances such as the following.

Duct detectors aren t a replacement for room sensors. 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. Therefore duct smoke detectors are typically considered mechanical equipment devices instead of life safety devices.

Where to place smoke detectors in the ductwork on commercial projects to comply with code. Testing air handling unit duct smoke detector. The detector shall be listed for the air velocity temperature and humidity anticipated at the point where it is installed.