Fire and Smoke Dampers 101
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According to the National Fire Protection Association (NFPA), smoke travels at 120-420 feet per minute (fpm) during an active fire. Thick, black smoke from a fire can fill a structure in mere minutes, and only a few breaths of the toxic smoke can cause unconsciousness or even death. Statistics show that 80% of all building related deaths are associated with smoke inhalation. Most victims are not located in the same room as the fire’s origin.
There are six predominant threats that loom from the threat of smoke. They are:
- Leading cause of firefighter injuries and fatalities
- Impedes visibility
- Can contain toxic unburned gases
- Fire consumes the oxygen in the air
- CO poisoning accounts for 50% of fatalities
- Can reach temperatures as high as 1300 degrees Celsius or 2370 degrees fahrenheit
To address this issue, fire and smoke dampers are used as a key component of a structure’s fire protection system. Dampers are typically installed in the fire-rated separation and become a part of the fire-rated wall system. Without fire and smoke dampers, smoke and fire can travel through rated walls via an open ductwork. In case of a fire, these devices act as the first line of defense to prevent flames, smoke, and toxins from spreading throughout a building. The most effective fire protection plans include detection, suppression and containment requiring both active and passive fire protection.
Active fire protection includes all systems designed to suppress or extinguish fire once it has started, as well as aid in the evacuation of occupants. These include smoke detectors, building pressurization, fire alarms, sprinklers, exit signs, and evacuation plans. However, active fire protection systems do not prevent the spread of smoke and toxic gases, the leading cause of death from fire.
Passive fire protection, however, is designed to prevent smoke, toxic gases, and fire from spreading; and by compartmentalizing fire, passive fire protection systems:
- Strengthen the effectiveness of active systems
- Facilitate occupant evacuation
- Protect property
- Minimize property damage
Compartmentalizing the building with fire-rated separations like fire walls, fire barriers, fire partitions, smoke barriers, and smoke partitions is a critical feature of the system. When penetrating these walls or partitions by the ductwork of the heating, ventilation, or air conditioning (HVAC) system, the integrity of their ratings are sustained by the use of fire dampers, smoke dampers, or combination fire/smoke dampers. These three damper types perform different functions and are installed and maintained differently as well. Knowledge of these differences is imperative to the proper application of the dampers and their performance in the life/safety system. Because dampers serve such a vital safety role, it is extremely important to keep dampers up to code and functioning properly.
What are Fire and Smoke Dampers?
Dampers fall into five types, each with a specific function. Types of dampers include fire dampers, smoke dampers, combination fire-smoke dampers, ceiling radiation dampers and corridor dampers. Their functions vary depending on the damper type.
Fire dampers are used to restrict the spread of fire where ducts and air transfer openings penetrate firewalls, fire barriers, fire partitions, horizontal assemblies and shaft enclosures. They can also be employed in air transfer openings in walls and partitions. The building codes specify where fire dampers are required.
Per the Air Movement and Control International Association (AMCA), “A fire damper can be defined as “a device installed in ducts and air transfer opening of an air distribution or smoke control system designed to close automatically upon detection of heat. It also serves to interrupt migratory airflow, resist the passage of flame, and maintain the integrity of the fire rated separation.” Its primary function is to prevent the passage of flame from one side of a fire-rated separation to the other.”
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. In addition to an hour fire-protection ratings, fire dampers for use in dynamic systems are also provided with an airflow rating which indicates the maximum velocity and static pressure that the damper is designed for.
Static Fire Dampers – Are installed in duct systems or penetrations where the HVAC system is automatically shut down 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.
These two types of fire dampers are certified by Underwriter’s Laboratory to carry an hourly fire-protection rating, usually 1 ½ – 3 hours:
Smoke dampers are used to restrict the movement of smoke where ducts and air transfer openings penetrate assemblies that are designed to restrict the movement of smoke. Per AMCA, Smoke dampers (Figure 3) are defined as “ The device operates automatically and is controlled by a smoke detection system. They can be opened or closed from a remote fire command station if required.” Their primary function is to prevent the passage of smoke through the heating, ventilation, and air conditioning system, or from one side of a fire-rated separation to the other.”
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
By utilizing a low voltage signal, the actuator places the damper at any point between fully open and fully closed. A critical element of an HVAC system, proper actuators ensure that dampers function properly – without them, the dampers won’t function at all. Damaged actuators lead to a degradation of system performance which causes energy waste, occupant discomfort, loss of time and increased labor costs. Proper maintenance and inspection of fire and smoke dampers, ensure that the actuators are in proper working order and functioning as they are intended.
Combination Fire-Smoke dampers
Combination fire-smoke dampers are used to restrict the spread of fire and movement of smoke where ducts and air transfer opening penetrate assemblies that are designed to restrict the passage of both fire and smoke. Dampers that are marked as combination dampers comply with UL’s standard for fire dampers and their standard for Smoke Dampers.
Ceiling Radiation Dampers
Ceiling radiation dampers are used to limit the passage of heat in fire-resistance-rated floor-ceiling or roof-ceiling assemblies. Ceiling radiation dampers are intended to function only as heat barriers to limit heat transfer into the concealed space of a floor-ceiling or roof-ceiling assembly.
Corridor dampers are combination fire-smoke dampers that have been evaluated for mounting only in specific tunnel corridor ceiling construction. In most cases the ceiling construction of a tunnel corridor will be as required for the corridor walls.
The importance of maintaining these dampers is critical to ensure that the building’s overall fire protection system is working properly. Fire damper inspections and smoke damper inspections are required by NFPA 80 and 105 every six years in healthcare facilities and every four years in non-healthcare facilities. To learn more about the inspection and maintenance of fire and smoke dampers, consider taking our online course to learn how to inspect these important facility assets. Still have questions? Contact us – we’d love to talk!