Life Safety in HVAC - What is a Fire Damper?

Life Safety in HVAC - What is a Fire Damper?

What is a fire damper? A fire damper is a damper that closes off penetrations in fire-rated barriers. Learn more about fire dampers in this Newsstand article. 

Life Safety in HVAC

A line of life safety dampers

HVAC systems will often require several types of dampers to meet the system’s requirements, but not all requirements will involve system performance. There will also be safety requirements that the system must meet.

“Life safety damper” is the common name for dampers that are built and tested to meet these requirements. Life safety dampers include fire dampers, smoke dampers, combination fire-smoke dampers, and ceiling radiation dampers. These dampers will be required at key points throughout the building, to slow the spread of fire and smoke. Your HVAC system must be prepared for an emergency.

 

What is a Fire Damper?

A fire damper is a life safety damper built and tested to hinder the spread of flames. Fire dampers are installed in fire barriers where ductwork or a ventilation opening passes through the barrier. These points are known as penetrations because they penetrate the barrier and leave an opening for flames to pass from one side of the barrier to another. 

Curtain fire damper beside a fire

Fire dampers are designed and tested to withstand intense heat.

Therefore, building codes will require fire dampers at these barrier penetrations to hinder the spread of fire through the penetrations in the fire barrier.

 

Fire Dampers and Heat Response Devices (HRDs)

Standard control dampers will open and close throughout the day to keep air moving through ductwork, but fire dampers remain open until they are needed. Fire dampers are designed to close automatically when a fire event occurs. They do this with help from a heat response device, or HRD. Heat response devices are temperature sensitive mechanisms, designed to activate under intense heat. Fusible links melt under intense heat, while thermo discs expand as temperatures rise. These devices provide the means to react to a fire event.

Round curtain fire damper with a fusible link

Pictured: The fusible link holds the curtain blade in place. When it melts, the link will break apart and release the blade.

The exact activation method will differ based on the HRD used for the damper. Fusible links are the most common heat response device. Fusible links are tied directly to the damper's blade and break apart at elevated temperatures. When broken, the link releases the blades from their fully open position. The blades return to the closed position, either by falling into place or through spring driven motion.

Thermo discs are HRDs incorporated into the circuitry of an electric actuator. The discs are part of the electrical circuit. These discs expand when exposed to elevated temperatures. When this happens, the thermo disc breaks the electrical circuit, cutting off power to the actuator. With no power, the actuator will close the damper by utilizing internal springs. This action is referred to as "power open, spring closed".

The key is response time. Fire dampers must close the moment a fire breaks out. Once closed, the damper will remain closed to hinder the spread of flames through the penetration. They will only reopen when operated by a technician once the fire event has ended. Technicians will determine if the damper is fit to be reused in the barrier, but fire dampers are commonly replaced to ensure they are in excellent condition.

 

Testing Fire Dampers

Fire dampers must undergo rigorous testing and adhere to stringent codes before they are approved for use in a fire barrier. Fire endurance testing is just one of several tests that a fire damper must complete to receive a fire-resistance rating.

In this test, the damper is installed in the opening of a test oven according to the manufacturer’s installation instructions. The fire damper is set to fully open, and the blades are held in place with a heat response device. Fusible links are the most common heat response devices because they are cheap and easy to replace. Then, the test oven is engaged, and the fire damper will close in reaction to the elevated heat.

Illustration of a fire damper undergoing fire resistance testing

The fire damper must remain closed and locked until the end of the test. Depending on the intended rating, the fire endurance test will run for 90 minutes (1.5 hours) or 180 minutes (3 hours), with temperatures reaching more than 1700 degrees Fahrenheit. The damper must not fail or allow flames past the damper. This testing ensures that the damper remains intact and keeps the penetration covered during a fire.

After the end of the fire endurance test, the damper will undergo additional testing, including duct impact testing. Duct impact tests ensure the fire damper remains in the barrier even if connected ductwork is compromised by falling debris. Once the fire damper has passed all these tests, the damper model will receive a fire resistance rating according to the fire endurance test completed: either 1.5 hours or 3 hours of fire resistance.

 

The Purpose of Fire Dampers

The purpose of fire dampers is to cover the penetrations found in fire-rated barriers, which compartmentalize a building during a fire event. As part of a fire-rated assembly, fire dampers can help occupants when a fire breaks out by hindering the passage of flames through the penetrations in the barrier. Passive fire protection, like fire dampers and other life safety dampers, are in place to buy time for occupants to safely evacuate the building.

Three different kinds of fire dampers

There are several fire damper types for various applications, but they all serve the same purpose: passive fire protection.

Looking to add fire dampers to your next project? Contact Air Balance today. We build static and dynamic fire dampers to fit your needs. Trust a brand with over 50 years of experience in meeting NFPA and UL requirements for fire safety in HVAC. Start your next project with life safety dampers built for the task.

 

Learn more about dampers and HVAC equipment with these Newsstand articles:

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