Failing dampers

Fire and smoke dampers must pass a rigorous series of tests prior to installation in a fire life safety building system with further requirements for how they are installed. However, even with excellent installation, regular maintenance and inspection of the dampers is necessary to ensure optimal performance. Any number of factors might lead to damper malfunction which are discovered only through the inspection process, or worse, upon failure during an FLS event.

Three of the most common factors are illustrated here, including: obstruction, failed linkage and failed actuator.


Obstruction is one of the most common factors contributing to damper failure. Obstruction can be caused by something as minor as dust build-up or as significant as another trade installing its materials through damper openings.

Communications wire bundle installed through a fire damper, preventing closure of damper.

Fire alarm conduit installed through smoke damper, preventing damper closure.

Failed fire and smoke damper held open by a rock.

Failed Linkage

Fire dampers are held open by fusible links. A fusible link is rated specifically for temperatures indicative of fire, above the design ambient temperature of the HVAC system. If a fusible link breaks and is not replaced with the proper rated component, the fire damper may fail to close under fire conditions.

Fire damper with missing fusible link held open with plastic zip tie.

Linkage connects a motor or spring to the damper axle or shaft, transferring the force to rotate the damper open or closed. Linkages can work loose over time or break, causing failure of damper movement when needed.

Linkage disconnected from actuator.

These dampers closed and then did not re-open during a standard FLS control actuation. The FLS control panel showed the dampers closing correctly and then re-opening correctly; however, the actual damper was still closed. After a complaint of low air flow, a maintenance worker found the damper closed and pried a section of the damper assembly open. During the process, the FLS control panel showed no alarm or fault. This is a clear example of the reasoning for a visual inspection, as a remote inspection can fail.

Failed Actuator

Actuators provide the power component to rotate dampers open or closed. Failure of an actuator causes failure of a damper to rotate as needed during a fire life safety event.

Actuator unwired and unsecured on damper.