Fire Damper

Fire dampers are safety devices found in the ductwork of buildings. Their main job is to stop fire and smoke from spreading through the ventilation system. Think of them as gatekeepers; when a fire starts and the temperature gets really high, these dampers automatically shut, blocking the path of the flames and smoke. This helps keep the fire contained to one area, giving people more time to evacuate and helping firefighters do their job. They’re a crucial part of a building’s fire safety system, making sure that the ventilation ducts don’t become a highway for fire and smoke.

Uses for fire dampers include air transfer apertures, ducts, and other penetrations into fire-rated structures (such as walls, floors, or other fire barriers). The property would be damaged, individuals working or visiting this area would be at risk, and the fire would quickly spread to other areas if these openings weren’t guarded. Aiming to contain the fire at its source and stop it from spreading to other areas, compartmentation is the strategy. In doing so, the fire’s spread and intensity are reduced, and the overall harm to the building and surrounding area is decreased.

Operation of fire dampers

Fire dampers operate through a combination of mechanical and thermal mechanisms to ensure they effectively close off air ducts during a fire. Here’s how they work:

1. Normal Operation: Under regular conditions, fire dampers remain open to allow air to flow freely through the HVAC system.

2. Activation:

   • Thermal Link: The fire damper is equipped with a fusible link or a thermal sensor. The fusible link is designed to melt at a specific temperature, usually around 165°F (74°C).
   • Actuation: When the temperature in the ductwork reaches the threshold due to a fire, the fusible link melts, triggering the damper to close. Alternatively, some fire dampers are connected to a fire alarm system and can be electrically actuated.

3. Closing Mechanism:

   • Gravity: In some fire dampers, gravity causes the blades of the damper to fall into the closed position when the fusible link melts.
   • Spring-Loaded: Other fire dampers use spring-loaded mechanisms that force the damper blades shut when the fusible link melts or the actuator is triggered.

4. Sealing: Once closed, the fire damper forms a barrier that blocks the passage of air, flames, and smoke. This helps to contain the fire to its origin and prevents it from spreading through the ventilation system to other parts of the building.

5. Resetting: After a fire event, fire dampers need to be inspected and reset or replaced to ensure they are ready for operation again. The fusible links or actuators will need to be replaced if they were activated.

Components for fire dampers

Fire dampers consist of several key components that work together to ensure their proper operation during a fire event. Here are the primary components:

1. Frame: The outer structure that houses the damper. It provides the support and attachment points for other components.

2. Blades: These are the parts that actually block the duct when the damper is closed. They can be of various designs, such as multi-blade or single-blade, depending on the damper type.

3. Fusible Link: A critical component that holds the blades open during normal operation. It melts at a specific temperature, triggering the blades to close. The melting point is usually around 165°F (74°C) or higher, depending on the specific requirements.

4. Actuator: In motorized fire dampers, an actuator (electric or pneumatic) is used to close the damper blades. It can be activated by a signal from the building’s fire alarm system or by a thermal sensor.

5. Thermal Sensor: This device detects high temperatures and can trigger the actuator to close the damper. It provides an additional method of activation beyond the fusible link.

6. Spring Mechanism: Many fire dampers use a spring mechanism to ensure that the blades close quickly and securely when activated. The spring forces the blades into the closed position once the fusible link melts or the actuator is triggered.

7. Blade Seals: These are materials attached to the edges of the blades to ensure a tight seal when the damper is closed, preventing the passage of smoke and hot gases.

8. Bearings: These are used to support the blade pivot points and ensure smooth operation of the damper blades.

9. Locking Device: Some fire dampers have a locking device that keeps the blades securely closed once they have been triggered.

10. Indicator Switch: This optional component can be used to provide a signal to a building management system, indicating whether the damper is open or closed.

11. Mounting Angles/Flanges: These are used to securely install the fire damper within the ductwork.