Whether you are a facility manager or a technician who works in or around ducting, you need to know how smoke and fire dampers work. Inspecting your dampers is a critical part of fire barrier management. If the dampers aren’t working, a fire in your facility has the potential of doing significantly more damage and will put patients and employees at far greater risk. Knowing what your dampers do and how they are supposed to operate is the first step towards better suppressing fires.
Dampers are like fire doors, but for your air ducts. In the event of a fire, they will close automatically and seal off the penetration created in the fire or smoke barrier that the duct creates. When the damper is closed, it is functionally a part of that barrier, creating an unbroken seal that will contain a fire within that suite of your facility. By containing the fire, these barriers make evacuation safer for the occupants of the building. Your active fire suppression systems, like your sprinklers, will also work better if the fire is not spreading. The part your dampers play in this system might seem small, but their role cannot be overstated.
To better understand how your fire and smoke dampers work, let’s separate them into categories based on what function they have.
Fire dampers are set within, you guessed it, firewalls where ductwork penetrates the barrier. They are held open by a fusible link, which is designed to melt and break apart when it reaches a specific temperature. When the link breaks, the curtain or louvers built into the fire damper will shut automatically, creating a seal and closing the fire barrier completely.
These dampers are further divided into the categories of static and dynamic. A static fire damper is designed to close when there is no airflow through the duct. This means that they are placed only in ducts that will have the airflow shut off by the air handler in the event of a fire. Because they do not have to resist airflow, static fire dampers can be shut either by gravity or by a spring.
Dynamic fire dampers are designed to close when there is airflow in the duct. They are always assisted by a rated spring that has been tested and is guaranteed to close the damper despite the resistance created by airflow. These can be installed whether or not the air handler will shut off airflow.
If your fire dampers aren’t working, there is a handful of possible causes. Often, the screws that were used to install the damper are placed in a way that prevents the curtain or louvers from closing properly. Sometimes the spring that should shut your damper is rusted or damaged. The fusible links that keep your fire dampers open can also break, leaving your damper closed. While this is fire safe, it can dramatically affect the airflow of your facility. Having a basic understanding of how your fire dampers are supposed to work will make it easy to diagnose what is preventing them from working properly.
Just like how fire dampers are operated when fire interacts with the fusible link, smoke dampers are activated when a smoke detection system sends the damper a signal. Smoke dampers are installed in smoke barriers and are operated by an actuator, which is an electric motor that rotates the louvers of the damper. Actuators are tied to smoke detectors and have their power toggled when smoke is detected. In certain facilities, they can also be activated remotely, either by switch or by a control system.
When smoke is detected, the actuator opens or closes the damper depending on its location. If the damper is set in a smoke barrier that divides suites, the damper will close and create a consistent barrier. However, some smoke dampers are set against exterior walls, and the actuator will open the damper to evacuate smoke from the building.
Because of the more complicated nature of smoke dampers, more things can prevent them from working. Smoke damper actuators can go bad and no longer operate the damper when powered. Bad actuators need to be replaced immediately. It’s also possible for the power supply to be faulty, or the smoke detector itself to be the cause of the problem. Like fire dampers, rust and misplaced screws can prevent a smoke damper from properly closing.
Combination Fire/Smoke Dampers
Combination fire/smoke dampers are exactly what they sound like: a damper that can be activated by both a temperature-sensitive device and a smoke detector. Functionally, these dampers operate the same way smoke dampers do: an electric actuator moves the louvers between the open and closed positions. However, these actuators are also tied to a temperature sensor. When these sensors detect a high enough temperature, it toggles the power going to the actuator.
Apart from the temperature sensor, a combination fire/smoke damper can be inspected the same way a smoke damper can. A simple heat gun can determine whether or not a temperature sensor is working properly.
At a Glance
Here is your no-nonsense guide to determining what kind of damper you’re looking at. Does the damper have a fusible link? If it does, you’re looking at a fire damper. Does the damper have an actuator? If so, it’s either a smoke damper or a combination fire/smoke damper. Do you see a temperature sensor attached to the actuator? If you do, that is a combination fire/smoke damper.
Why You Need to Stay Compliant
Whether or not your fire and smoke dampers are operational is a matter of life and death. The compartmentalization of your building is what allows occupants to safely evacuate in the event of a fire, and that compartmentalization can be compromised by even one non-functional damper. As a technician or facility manager, it is your responsibility to understand how your dampers work so that you can guarantee that they will work in the event of an emergency. By educating yourself and your teammates, you can maintain your dampers and be assured that your facility is as prepared as possible for a fire.
If your dampers are all working and a fire breaks out, the systems in place will do the heavy lifting for you. Your fire doors and dampers will shut, creating airtight fire and smoke barriers and keeping the fire contained. Because the fire isn’t spreading outside of that suite, occupants can exit the building according to the established emergency exit routes. Your valuable property will be protected, and the structural integrity of your building will remain uncompromised.
If even one damper is rusted or held open by a bad actuator, a fire can move from the suite it started in to another area, multiplying the damage and risk to human life that the fire poses.
Dampers in any building need to be formally inspected (with a report turned into your Authority Having Jurisdiction) every four years. If your facility is classified as a hospital, it will need to be inspected every six years. Likewise, any newly installed damper will need to be inspected one year later, and then every four to six years. Your facility will be held to the standards set by NFPA, to ensure that it is safe enough to occupy. You have a huge responsibility, not only to keep your dampers up to code, but to protect the lives of those who enter your building.
Fire and smoke dampers aren’t complicated. Just by reading this you’ve better prepared yourself to assess the condition of your dampers and keep them functional. You might only have a few dozen dampers to consider, or you might have thousands. No matter how daunting the task, maintaining your dampers is critical to the safety of everyone in your facility.