What Is the Difference Between Static and Dynamic Fire Dampers?

Static and dynamic fire dampers play a pivotal role in making all buildings better by safeguarding individual lives and properties as a whole. However, each type of damper carries unique characteristics, functionalities, and applications.

Because building safety can be complicated, understanding the differences between these two types of fire dampers is essential for architects, engineers, and safety professionals.

Static vs. dynamic fire dampers, outlining their characteristics, advantages, and limitations helps make informed decisions when selecting between critical fire safety components.

Understanding Fire Dampers in Building Safety

Fire dampers are safety devices integrated into a building's HVAC system that are designed to prevent the spread of fire through ductwork.

In the event of a fire, the dampers close and seal off the ducts in order to contain the fire within a limited area. Fire dampers are typically designed to remain closed until manually reset to the open position once the situation is safe. Their role is crucial in maintaining the structural integrity of the building and ensuring occupant safety during fire incidents.

What is the Difference Between Static and Dynamic Fire Dampers?

Fire dampers come in two main configurations: static and dynamic. While they both fulfill the same primary function of fire protection, they have different capabilities and are better suited for different applications.

Static fire dampers, as the name suggests, are designed to operate in HVAC systems that shut off during a fire. They close when the temperature in the ductwork reaches a certain threshold, typically via a fusible link that melts at high temperatures to trigger the closure mechanism. Static fire dampers are primarily used in systems where the HVAC system shuts down during a fire event.

Dynamic fire dampers are designed for HVAC systems that continue to operate during a fire or where a smoke control system keeps the HVAC system on to evacuate smoke. They can close against airflow to ensure that they effectively seal off the duct even when the air handling system is running. Dynamic dampers typically incorporate springs and more complex closure mechanisms to counteract the force of moving air. Static dampers do not have enough force to close against moving air which would cause them to stay open if used in an application that required a dynamic fire damper.

Advantages and Limitations of Static Fire Dampers

Static fire dampers are much simpler due to their fewer moving parts. They generally have a lower cost compared to dynamic dampers. Static fire dampers are effective in systems that automatically shut off during a fire since these systems will not have airflow that the fire damper must close against.

What makes static fire dampers simpler also limits their use to HVAC systems that stop airflow in a fire event. If used in a location that actually requires a dynamic fire damper, the fire damper may fail to operate when exposed to a fire. Static fire dampers may also not be suitable for high-velocity air systems as they typically rely only on the force of gravity to allow them to close.

Advantages and Limitations of Dynamic Fire Dampers

Dynamic fire dampers are suitable for HVAC systems that maintain airflow during a fire. They are capable of withstanding air velocities of 2000 fpm and static pressures of 4” w.g. due to the springs and other motive forces used in the dampers. Dynamic fire dampers can be ordered to operate at higher velocities and static pressures. They provide greater flexibility in HVAC system design and operation.

While dynamic fire dampers are more versatile, they are also more complex. They generally are more expensive than static dampers due to more complex mechanisms.

Static fire dampers have larger single and multi-section assemblies than dynamic dampers. Dynamic fire dampers are built in smaller sizes to be able to handle the air velocity and static pressures.

Fire dampers either static or dynamic, require maintenance and inspection every 4 years and hospitals every 6 years per NFPA 80.

How to Choose?

The choice between static and dynamic fire dampers depends largely on the specific requirements of the HVAC system and the building’s fire safety strategy. Static dampers are ideal for systems that cease operation in a fire, for a cost-effective and straightforward solution. Dynamic dampers, on the other hand, are necessary for systems with continuous airflow to provide reliable protection even under challenging conditions. Dynamic fire dampers can be utilized in static systems without voiding any building code ro UL listings.

Selecting the right fire damper involves considering many factors. The design and operation of the HVAC system is often the most important. The airflow velocity and pressure within the ductwork will determine the forces the damper may see. Building codes and fire safety regulations specific to the project often set the minimums that must be done. Cost implications and maintenance requirements are also significant drivers that should be taken into consideration.

Static and Dynamic Fire Dampers: Both Ready to Protect