Hvac Duct Smoke Detector Requirements

Duct smoke detection nfpa 90a code requirements there are exceptions to the two basic requirements.

Hvac duct smoke detector requirements.

A duct smoke detector should shut off a typical blower and fresh air and turn on the exhaust duct detectors aren t a replacement for room sensors 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. The automatic shutoff shall interrupt the power to the air moving system by the use of a smoke detector located in the main supply air duct. Duct smoke detectors are not required if the occupied space is served by an area smoke detector system. Therefore duct smoke detectors are typically considered mechanical equipment devices instead of life safety devices.

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. The ashrae handbook of smoke control engineering nfpa life safety book for health. Duct smoke detection may be useful in preventing injury and property dam age in instances such as the following. There are other smoke detector safety concerns in air conditioning and heater systems and they can be found in the following reference material.

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.