QUESTION: Are fire dampers required in ductwork when the duct penetrates the walls of the same room that house the air handler? These air handlers are equipped with duct detectors that shut the air handler system down and activate the alarm system.
ANSWER: It depends on the fire rating of the wall. NFPA 90A Standard for the Installation of Air-Conditioning and Ventilating Systems is very clear on this issue. Fire dampers are only required in the following situations:
- When the duct penetrates a 2-hour fire rated barrier
- When the duct penetrates any fire rated vertical shaft
- When a duct terminates at a 1-hour (or greater) fire rated barrier but the airflow continues through the barrier into an open air plenum ceiling space
The need for a fire damper is a result of the fire rating of the wall. The room that you describe (air handler room) is not necessarily a hazardous room by definition, unless you also have fossil fuel-fired devices (gas-fired boilers, incinerators, water heaters, etc.). If the walls of this room are not required to be fire rated, then the ductwork does not require fire dampers.
Perhaps you are thinking about smoke dampers in regards to air handlers. Smoke damper are required to be installed in air handler systems that have a capacity greater than 15,000 cubic feet per minute. The purpose of these smoke dampers is to isolate the air-handling equipment, including the filters, from the remainder of the system in order to restrict the circulation of smoke. There are exceptions to this smoke damper requirement on air-handler units: A). on air handlers that are located on the floor that it serves and only serving that floor, and: B). When the air handler unit is mounted on the roof and only serves the floor immediately below the roof.
In these situations, the smoke dampers are not necessarily required to be mounted in the wall of the air-handler room, but just in the ductwork at the discharge of the air-handler. Remember: The purpose of the smoke dampers is to isolate the air-handling equipment from the remainder of the ductwork distribution system.