Field Modifications of Fire, Smoke, and Combination Fire/Smoke Dampers

Mounting/Retaining Angles

The annular space between a damper and a barrier opening (Photo B) allows the damper to expand and work properly during high heat exposure. Typically, damper installation instructions require mounting angles on all four sides of a sleeve to cover the annular space and do not allow any materials to be installed in the annular space. When one side of a damper is too close to a ceiling, wall, or floor, the manufacturer may provide options for removing the mounting angles from that side of the damper. Where mounting angles have been removed, a firestop material or an intumescent caulk can be used to protect the through opening in a fire-rated barrier. Approved firestop materials and correct installation will be outlined in UL-approved installation instructions.

Sealants

Questions concerning gaps between mounting angles and rated barriers and how to seal them sometimes arise. The sealants approved for these applications will be listed in UL-approved installation instructions.

It is common for sealants approved for sleeve modifications also to be approved for sealing gaps between mounting angles and barriers. Note: These sealants typically are not allowed in the annular space between damper sleeves and openings; they are allowed where mounting angles touch a barrier.

Actuators

UL requires all actuators supplied on life-safety dampers to be factory-installed and cycle-tested prior to shipment. “Dampers Marking and Application Guide” (Page 12) states the following with regard to field modifications of actuators:

Smoke dampers and combination fire-smoke dampers are equipped with factory installed electric or pneumatic actuators which remotely control the dampers. The airflow and pressure ratings marked on the dampers are dependent upon the particular combination of damper type, actuator type and linkages between the damper blades and actuator. As such, field mounting or substitution of actuators is not covered within the scope of the UL certification of the product. However, this does not necessarily preclude replacement of actuators in the field. Like any appliance, field servicing of these products is not covered under the scope of the UL certification program. As with any part of the damper, it is expected that replacement of actuators in the field be done in accordance with the damper manufacturer’s normal field servicing program.

Prior to building commissioning, actuator replacement may be needed to accommodate a change in actuator voltage or to swap out an actuator without indication switches for one with indication switches. Often, replacements can be made without a change in actuator model and with little change in overall actuator configuration. More substantial modifications may be required if a different actuator model is needed or if an actuator has to be changed from mounted on the damper sleeve to mounted within the damper sleeve. Such modifications may require additional hardware to complete, so it is best to contact the manufacturer for guidance. Any actuator modifications should be done in accordance with manufacturer instructions and guidelines and, once completed, followed by damper cycling.

Because they are not covered under the UL certification program, actuator modifications may need to be reviewed and approved by the local AHJ.

Mullions

All life-safety dampers are certified to a maximum overall size. There are times, however, when an opening exceeds that size. This can be the case when an opening is larger than the furnace used in the testing and certification of a damper. In vertical wall applications, steel mullions can be used to divide an opening into sections. “Dampers Marking and Application Guide” outlines the use of mullions (Page 12):

In certain circumstances, steel mullions can be used to divide a large wall or vertical partition opening into smaller individual openings, allowing fire dampers for use in static systems to be sized and installed within the limitations of the certification. These mullions are generally fabricated in the field. Damper manufacturers can provide installation details covering the fabrication, installation and use of mullions.

Because airflow ratings of fire dampers for use in dynamic systems and combination fire-smoke dampers are size dependent, the use of the mullions discussed herein are only intended for application with fire dampers for use in static systems. Further, the mullions are limited to use in vertical partitions.

Fabrication and sizing of vertical steel mullions (Figure 2) are covered in UL-approved installation instructions. The mullions are approved for use with concrete-block, masonry, brick, or poured-concrete walls only. Additionally, they are approved for use with dampers with a fire-resistance rating of 1-1/2 hr, which can be installed in barriers rated for less than 3 hr.³

As the above excerpt states, UL recognizes the use of vertical mullions only in static systems, or systems that cut off airflow in the event of a fire. For dampers installed in dynamic systems, options allowing the use of mullions may be available. One possible option for dynamic systems involves splitting ductwork to make sure mullions do not experience the dynamic forces of the system when dampers close. The use of vertical mullions in dynamic systems requires approval from the local AHJ, who may need additional information from the architect and engineer of record.

“Dampers Marking and Application Guide” does not address the use of mullions in horizontal floor applications. The installation instructions of some manufacturers (Figure 3) do, however, and these instructions typically are UL-approved. Horizontal support mullions for dividing oversized floor openings—typically, concrete floors only—may vary from manufacturer to manufacturer, so it is important to review installation instructions for proper application, construction, and installation, as well as the mullions’ maximum fire-resistance rating. In some cases, mullions can be used with dampers having a fire-resistance rating of up to 3 hr. This allows the mullions and dampers to be installed in floors with a fire-resistance rating of more than 3 hr, as 3-hr-rated dampers can be used to protect openings in barriers rated for 3 or more hours.³

Damper Blades

For a fire- or a combination fire/smoke-rated damper to protect an opening in a fire-rated barrier, the blades of the damper must close within the barrier. Many manufacturers, however, have options for factory-supplied dampers with blades that close outside of a barrier. These dampers, which undergo additional testing, typically require an insulated blanket around the damper sleeve.

If a traditional damper needs to be installed outside of a fire-rated barrier (Figure 4), manufacturers have installation instructions detailing the materials needed to modify the damper. This type of modification falls outside of the UL certification service and typically requires approval from the local AHJ.

Summary

This article only begins to address the different types of modifications that may be needed for life-safety dampers to be installed successfully. With building conditions varying from site to site and the obstacles faced by installers often unforeseen, addressing all possible modifications is impossible.

Installation instructions vary by manufacturer. Thus, it is imperative that all supplied installation instructions be reviewed prior to, and followed during, the installation process. Another best practice is to cycle a damper after any modification is made to ensure the damper will function properly.

When conditions requiring modifications falling outside of manufacturer-supplied installation instructions arise, it always is a good idea to contact the manufacturer to determine the best path forward. In addition to providing guidance for the installer, the manufacturer can help the local AHJ understand the modifications that were performed and how those modifications apply to the damper’s installation, certification, and overall function.

References

1. UL. (2016). Dampers marking and application guide. Retrieved from https://bit.ly/Dampers_Marking
2. UL. (2011). Fire resistance, directory C. Northbrook, IL: Underwriters Laboratories.
3. ICC. (2017). 2018 international building code. Washington, DC: International Code Council.

About the Author

James Carlin is product manager, dampers, for Pottorff, a position he has held since 2015. The eight years prior to that, he was a design engineer developing UL-rated and air-control dampers for the company. A graduate of Stevens Institute of Technology with a bachelor’s degree in mechanical engineering, he chairs the AMCA Fire and Smoke Damper Subcommittee.