Question 1

What is a fire damper?

Accepted Answer

A fire damper is a passive fire protection device installed inside an air ductwork system at the point where the duct penetrates a fire compartment wall or floor. When a fire occurs, the fire damper automatically closes to seal the duct and prevent flames, hot gases, and smoke from travelling through the ventilation system from the fire compartment to other parts of the building. Ventilation ductwork is typically continuous across multiple compartments - the ducts pass through compartment walls to supply or extract air from different areas. Without fire dampers at each compartment wall penetration, the duct would create a hole in the compartmentation, allowing fire to spread freely. A fire damper restores the integrity of the compartment wall at the duct penetration location. Fire dampers are required by Building Regulations Approved Document B wherever a duct passes through a fire compartment boundary, subject to minimum duct size thresholds.

Question 2

How does a fire damper work?

Accepted Answer

A standard fire damper uses a fusible link to trigger closure. The fusible link is a small heat-sensitive element (typically a low-melting-point alloy or a spring held compressed by a thermoplastic material) installed within the ductwork airflow. During normal operation, the damper blades are held open by the fusible link, allowing air to flow freely through the duct. When a fire heats the air in the duct to the trigger temperature (typically 72 degrees C), the fusible link melts or releases, and a spring mechanism closes the damper blades (or drops a curtain across the duct opening), sealing it against fire passage. The damper must be capable of operating despite the fire-induced airflow pressure in the duct and must maintain its integrity for the rated period. Electrically-actuated dampers can also be triggered by the fire alarm system, allowing remote closure before the fire reaches the damper - this is common in larger buildings with sophisticated fire control systems.

Question 3

What is the difference between a fire damper and a smoke damper?

Accepted Answer

A fire damper and a smoke damper address different aspects of the fire spread risk through ductwork. A fire damper is designed to prevent the passage of flames and hot gases through a duct at a fire compartment boundary - it closes at a relatively high trigger temperature (typically 72 degrees C) and must maintain fire resistance integrity for the rated period. A smoke damper is designed to control the spread of smoke through the ventilation system - it typically closes at a lower trigger temperature or, more commonly, is controlled by the fire alarm and smoke detection system, closing when smoke is detected in the duct rather than waiting for high temperatures. A combined fire and smoke damper performs both functions. Building Regulations Approved Document B specifies where each type is required; in most non-domestic buildings with mechanical ventilation, the fire engineer or services engineer will specify the correct type for each duct penetration based on the building's fire strategy.

Question 4

How often do fire dampers need to be tested?

Accepted Answer

Fire dampers must be tested regularly to ensure they will operate when needed - a damper that has seized in the open position due to corrosion, debris accumulation, or mechanical failure provides no protection. BS 9999 (Code of practice for fire safety in the design, management and use of buildings) recommends that fire dampers are tested every 12 months in most buildings, and every 6 months in high-risk buildings (kitchens, dusty or corrosive environments). The test involves triggering the damper (typically by releasing the fusible link or operating the electrical actuator) to verify that it closes fully, checking that the blades or curtain seat properly, and then resetting the damper and verifying it reopens to the correct position. Access must be provided to each damper for testing - this must be designed in at the installation stage, as testing is impossible if dampers are inaccessible. Many fire dampers in older buildings have never been tested since installation because access was never provided.

Fire Damper

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