How Do Fire Dampers Work?

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How Do Fire Dampers Work?

In general, a fire damper works when the heat from the fire causes the normal temperature of a room to rise to about 74°Celsius. The fusible link attached to the damper would then melt, causing the damper’s door to close. In rooms where the normal temperature of the room is consistently higher, a higher degree fusible link would be attached to the damper. These particular fusible links would melt at a temperature about 100°Celcius. There are two types of fire damper designs used to help prevent the spread of flames, a dynamic fire damper and a static fire damper.

Dynamic fire dampers:

Dynamic Fire Dampers are located in vertical barriers, where the HVAC system fan will stay on in the event of a fire. Because they are installed in vertical barriers, these particular fire dampers have a spring-loaded design. The spring-loaded design is where the doors of the damper have a spring like action when they are forced to shut. Since the HVAC system fan will remain on, the air pressure from the fan will help the doors of the damper to spring shut.

Static fire dampers:

Static Fire Dampers are located in barriers where the HVAC system fan will shut off in the event of a fire. These particular fire dampers would be installed in horizontal barriers, and would have a curtain like design. Since the HVAC system fan will turn off, there would be no air pressure and the door of the damper will fall due to gravity.

Understanding how do fire damper works can help you have a better understand of why inspecting and repairing fire dampers are so strictly enforced. It only takes about 30 seconds for a small flame to grow and become a major fire. By cutting off the passageways for flames to travel, the fire will be contained to one specific location.  With the holidays on their merry way, making sure that your facility is fire prepared is essential.

It may not seem like a big deal, especially with other fire protection features put in place. But fire and smoke can spread quickly, and one of the best ways for a smoke and flames to completely engulf a building is through the ventilation system. That’s why dampers have been specifically designed to help contain the fire as well as smoke to keep occupants safe while preventing unnecessary property damage. And as a facility manager you consistently hear that you need to have your facility’s fire and smoke dampers inspected and repaired. There are tons of great articles about the top reasons why dampers fail and how often they need to be inspected. It’s all important information, but here is what you should know about the actual dampers themselves?

There are three different kinds of dampers – fire dampers, smoke dampers, and combination dampers.

Fire dampers prevent the spread of fire within the ductwork through fire-resistance rated walls and floors. They work when the heat from the fire causes the normal temperature of a room to rise to about 74°Celsius. That heat causes the fusible link, which is holding the damper open, to melt and allows the damper to be closed. There are two types of fire dampers:

  • Dynamic Fire Dampers – Are installed in vertical barriers, where the HVAC system fan will continue to blow in the event of a fire. Because the fan will stay on, the spring- loaded design helps the damper to spring shut against the air pressure.
  • Static Fire Dampers – Are installed in barriers where the HVAC system fan will shut off in the event of a fire. Because the fan will turn off, these dampers are designed like a curtain, allowing the damper to fall and shut due to gravity.

Smoke dampers resist the passage of air and smoke within the ductwork. They are typically operated by a smoke detector, which would also be located in the duct. Once smoke has been detected, the smoke detector sends a signal to the dampers’ actuator, which uses the jackshaft and linkage to open and close the blades of the smoke damper. There are two types of actuators:

  • Pneumatic Actuators – Need air to function properly
  • Electrical Actuators – Need power to function properly

To get the best of both worlds, combination dampers are used in areas where both fire and smoke barriers are located to prevent the passage of both fire and smoke between areas.

Dampers are a key component to your campuses overall fire and life safety plan. They help prevent the spread of fire and smoke by blocking access through the facility’s ventilation system. However, this means dampers are hidden from view, which means they are less likely to be though about. Dampers also have a tendency to frequently fail, which is why they must be maintained on a routine basis. According to the National Fire Protection Association (NFPA), “Each damper shall be tested and inspected one year after installation” and “The test and inspection frequency shall then be every 5 years”.