When fire strikes, the last thing we want to consider is how our HVAC (heating, venting, and air-conditioning) system, including fire dampers, works to stop the spread. But we are beyond grateful that it operates in such a manner to slow down and stop the fire from creating a mass casualty event, thanks to a simple little item called a fire damper. So, what is a fire damper, and how does it work to protect us? Let’s check it out.
What is a Fire Damper?
A fire damper is a type of HVAC damper that, in the case of fire, will activate to stop the continuation of fire and smoke in the ductwork. These dampers have been essential to buildings’ fire protection design since 1939. It was at that point that the National Board of Fire Underwriters understood the importance of having an HVAC damper that would automatically close in the presence of fire and smoke and activate an automatic fan shutdown if required.
Since then, engineers have ensured fire dampers and smoke dampers are an integral part of their HVAC damper design. Fire dampers are critical safety devices that can prevent flames and smoke from spreading through a building via the HVAC system.
7 Things to Learn About Fire Dampers
1. Fire dampers are needed in every HVAC system.
2. Not everyone can manufacture them.
3. Static dampers are used with systems where fans turn off.
4. Dynamic dampers are used with systems where fans stay on.
5. Curtain type is the most common.
6. Multi-blade damper is another type.
7. They need to be checked.
1. Fire dampers are an integral part of your HVAC fire protection plan
When your home or building HVAC system was developed, dampers may have been a required component. To maintain the necessary fire rating for the walls, partitions, barriers, or floors when ducts have openings penetrate them, certain building codes and regulations require that fire dampers are installed to provide, in the event of a fire, a necessary separation to restrict the fire from spreading.
2. Fire dampers need to be made to specific requirements
Only those companies and manufacturers that can demonstrate that they can design and manufacture them according to specific requirements dictated by the Underwriter Laboratories (UL) Standards are permitted to make them. These standards are referred to as Standard UL 555, The Standard for Fire Dampers. Underwriter Laboratories is a company that provides the world with global safety standards for science and engineering.
3. One kind of fire damper is a static fire damper
These dampers are utilized to close when the airflow of the HVAC system has been turned off when there is a fire.
4. Another type of fire damper is a dynamic fire damper
These fire dampers are designed for HVAC networks that need the damper to close while still under pressure (while the system has the fans running), even during a fire or smoke event.
5. Curtain-type fire dampers are the most common for their ease
Curtain-type fire dampers, also known as fusible link fire dampers, are the most common dampers used in HVAC systems. These tend to be installed the most due to their ease of installation and cost-effectiveness. Also, because they have fewer blades, there are fewer to restrict airflow and cause resistance to the HVAC system.
They operate by virtue of the fusible link. When fire reaches the fusible link or the temperature reaches a set level; generally, 165 degrees Fahrenheit (or higher, if the fire dampers are used in a high-heat environment, such as a kitchen or laundromat), the link will break or melt, releasing the curtain, and the damper will close.
These dampers are very effective, but there are some downsides, including:
- Need to be manually reset
- Have been known to jam
- Only rated to be used in HVAC systems that have all fans turned off during a fire
- Can only be used in smaller ducts
6. A second type is multi-blade fire dampers
Similar to curtain-type fire dampers, the multi-blade dampers utilize a fusible link to close in the event of a fire. When the size of the ducts doesn’t allow the use of a curtain-type fire damper, you will need to install the multi-blade type. These can be used in dynamic HVAC systems, where the airflow will need to remain on even when a fire occurs. The multi-blade fire damper can also be used on larger HVAC duct installations.
There are two potential downsides to using the multi-blade fire damper. One is the need to manually reset because of the difficulty in reaching the damper if care was not taken to make access a priority when designing the HVAC system. Two is the potential for the multi-blades to create resistance to the regular airflow of the system.
7. Fire dampers need to be inspected regularly
Making sure to install dampers is only one step of your fire protection plan. One year after you have had your dampers installed in your HVAC system, you should have them inspected. After that initial inspection, you should have follow-ups done every four years. There are variations, such as in hospitals, where the inspections will be done every six years instead.
What is a Fusible Link?
A fusible link is a mechanism that will hold the damper blades of the fire damper in the open position. Once the fusible link is exposed to the temperature set point, the surround will melt or break apart, and the fusible link will open. Once the fusible link opens, the damper blades close, preventing the fire or smoke from moving through your ducts. Once activated, they will need to be replaced manually.
As before, Underwriters Laboratories has a standard for fusible links and their manufacture. UL 33, the standard for heat-responsive links for Fire-Protection, ensures that all thermal links have been tested for sustainability and reliability via oven tests, oil bath tests, corrosion, and load tests.
Fire dampers are a seemingly small part of your HVAC system, yet they play a massive part in your overall fire protection plan. Making sure you have the right pieces for your HVAC plan is essential, and we at Lloyd Industries are here to help you every step of the way. Don’t hesitate to contact us for any of your HVAC needs. Require a contractor or technician? Check out our vetted list of professionals in your area!
