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Life Safety Dampers - Important Tests for Fire Dampers

In this article, we discuss the important tests required for every fire damper, per UL Standard 555. These tests ensure that all fire dampers will fulfill their intended purpose during an emergency: containing flames to a specific area and preventing them from spreading.

As part of a passive fire protection system, fire dampers contain flames to specific pre-defined compartments. These compartments slow the spread of flames to other parts of the building and buy occupants precious time to evacuate the building.

All life safety dampers must be qualified by the Underwriters Laboratories (UL), or an equivalent certifying agency, to be approved for use in a passive fire protection system.

As part of UL Standard 555, fire dampers and their components are required to pass eight tests:

  • Fire endurance test
  • Hose stream test
  • Salt-spray exposure test
  • Spring closing force test
  • Long term holding test
  • Hydrostatic strength test
  • Dynamic closure test
  • Duct impact test

All these tests are performed by UL-approved laboratories with approved equipment and testing methods.


Fire Endurance Test

Fire dampers are mounted in a test oven and subjected to intense heat.The fire endurance test will determine the damper’s fire resistance rating, which is expressed in hours of time. Fire barriers and their individual components will all have fire resistance ratings. If a fire barrier is rated under two hours, and is ducted, then it does not require a fire damper in its penetrations. Otherwise, if the rating exceeds two hours, then the barrier will require a fire damper with a fire resistance rating of 1½ or 3 hours.

For the fire endurance test, the test damper is mounted onto a test oven in the intended install orientation (either horizontal or vertical). This setup emulates a fire damper installed in a barrier during a fire. Testers will follow the manufacturer’s installation instructions for the test substrate when mounting the damper in place. This method ensures that the test damper is installed in the same way it will be installed in the field.

Once in place, the damper is set to the open position and the fire is ignited. The damper must close with its heat response device, as it would during a fire event. When the damper closes, it must remain locked and intact for up to three hours in fire conditions.

The test duration and the maximum temperature will depend on the damper’s intended fire rating. For instance, a 1½-hour rated fire damper will be tested for 1½ hours. The damper must stay intact for the duration of the test, as temperatures in the test oven reach 1792°F. A 3-hour rated damper must withstand temperatures up to 1925°F for three hours. The damper will fail the fire endurance test if it breaks down before its intended time.


Hose Stream Test

The hose stream test is administered immediately after the fire endurance test. This test will determine if the damper remains closed and intact during explosive fire conditions. If a fire damper warps beyond a certain threshold or its blades become open, it will allow flames to pass through. For the test, the super-heated damper is sprayed with water from a hose.

The super-heated fire damper is subjected to water spray from a hose, to test material warpage and resilience.

Pictured: An illustration of a curtain fire damper receiving the hose stream test. The damper will remain super heated from the fire endurance test.

Water is discharged from a 1⅛” nozzle at 30 PSI for a 1½-hour rated damper or 45 PSI for a 3-hour rated damper. The hose stream test utilizes a prescribed spray pattern and duration, based on the total area of the damper. The damper will fail this test if the locking mechanism fails or any components warps past a given tolerance:

  • Warping in excess of ⅜” between the blade edges and the damper’s frame,
  • ½” of warping, or more, between blades,
  • Or ⅛” of warping between the damper’s frame and its sleeve.

If the damper remains closed and intact, then the damper will pass the hose stream test.


Salt Spray Test

The salt spray test simulates the build up of dust and dirt as a damper operates inside a duct.In the salt spray test, the fire damper is installed in a testing chamber using the manufacturer’s installation instructions and in the intended orientation (horizontal or vertical). Once installed, the damper is subjected to a continuous salt spray for 120 hours.

The salt spray test simulates the build up of dirt and airborne debris on the damper. This build up can be cleaned away with regular maintenance, but it must never hinder the damper.

At the end of the test, the test damper is removed from the chamber and dried for 24 hours. After the drying period, the damper must be able to close and lock to pass the test.


Spring Closing Force Test

The spring closing force test will measure the amount of force exerted by the springs used in static-rated fire dampers. Static-rated dampers are only guaranteed to close when there is no air flowing through the duct. These dampers will utilize springs to force the damper's blades to the closed position.

To pass this test, these springs must be able to exert 2½ times the force required to close the damper.


Long-term Holding Torque Test & Hydrostatic Strength Test

An electric actuator must stay continually powered on for 6 months, then move to the closed position when powered down.Electric actuators on fire dampers are configured to remain open while the actuator is powered and close the moment it loses power. Each electric actuator is required to pass a long-term holding torque test.

Sample actuators are set to their powered position – to open the damper – and must stay in this state for 4,320 hours (or 6 months). After this duration, power is cut to the actuator. It must return to its unpowered position, closing the damper.

Pneumatic actuators must withstand an internal air pressure of five times its standard limit, and hold that pressure without bursting.Pneumatic actuators will undergo a hydrostatic strength test. Sample actuators are subjected to an air pressure that is five times its limit for 60 seconds. During the test, the actuator must not leak or rupture. If it stays in one piece, then the actuator passes the test.

Once they pass the test, actuators are approved for use on life safety dampers.


Cycling and Dynamic Closure Test

Life safety dampers rated for dynamic air conditions must undergo a cycling and dynamic closure test. This test is performed on an assembly of several sample dampers, known as panels. To begin, each panel in the assembly is individually cycled open and closed for 250 intervals.

After successful cycling, the damper assembly begins the dynamic closure test. Each panel is closed against an air stream flowing at a given minimum velocity and closure pressure. The damper panel must close three times at ambient conditions and once at an elevated temperature.

During the elevated temperature test, the damper’s heat response device must be activated to close the damper. The four test intervals are repeated with air flow in the opposite direction, for a total of six ambient closures and two elevated temperature closures.

A static closure versus a dynamic closure. Dynamic closures can occur while fans are on.

The left image depicts a static closure: the fans in the system are off and the damper closes without resistance from airflow. The right image depicts a dynamic closure: the fans will be running during an emergency. The damper needs to close, even if the fans are still running.


Duct Impact Test

This is the duct impact test. A fire damper must remain in the fire barrier, even if connected ductwork fails.Break-away connections are specialized parts connecting the damper sleeve to the duct. During a fire, break-away connections will separate the duct from the damper. This action prevents the damper from being dislodged from its anchorage in the fire barrier. Each fire damper is subjected to a duct impact test to guarantee all its break-away duct connections properly separate the damper from failing duct work. 

For the test, the damper is installed in a partition in accordance with the manufacturer’s installation instructions and connected to a test duct via break-away duct connections.

A weighted barrel is dropped onto the test duct to simulate falling debris. The barrel’s weight will vary based on the size of the test damper:

  • Test barrel weighs 275 lbs. for dampers 24” x 24” or smaller
  • Test barrel weighs 400 lbs. for dampers larger than 24” x 24”.

Once the barrel drops, the damper must complete three cycles with the blades fully closed and locked in position. Once complete, the damper will pass the duct impact test.


Certified Fire Damper

With all tests complete, the fire damper will be certified by UL for use in a passive fire protection. Each fire damper will receive a label that contains the product's UL file number. You can also find this file number on the product's submittal. Each of these tests is designed to make sure the damper performs its intended function when needed. Fire dampers, and all life safety dampers, are there to protect the most important part of your building: the people inside.

Life safety dampers are designed to protect the most important part of your building: the people inside.


MCDLG & Continuing Education

MCDLG offers free self-paced courses online through AEC Daily.

Our UL Damper course, Fire & Smoke Protection with Life Safety Dampers, goes over all of the basic stats, terms, and principles involved in choosing life safety dampers for your passive fire protection system.

Visit AEC Daily to browse our online courses

This course provides continuing education credits for a variety of institutions, including ASHRAE's PDUs. Learn the basics of UL dampers and earn credit, at your own pace. Visit the MCDLG course page on today!

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