Air control or smoke control? Which do you need for your project? In this article, we compare control dampers with smoke dampers. Learn more on the MCDLG Newsstand.
Have you ever thought about using a control damper for smoke control applications? It should work in theory, right? This is a big mistake, of course. In this damper showdown, we will compare these two damper types and help clarify why smoke dampers are best for smoke control.
Control dampers and smoke dampers look the same. They both have multiple blades – either single-thickness or airfoil – that rotate on axles. Both dampers open and close by rotating their blades. To spot the difference, check the blade seals.
Air control dampers will have clear or white seals along the edges of each blade. Airfoil blade seals are in grooves slightly off from the edge, so that they are hidden when the damper is fully closed. You may need to see the damper in the fully open position to spot them. Smoke dampers will have orange blade seals.
Manufacturers will typically use vinyl or silicone rubber seals for air control dampers. These seals are heat resistant to 120 degrees Celsius (248 degrees Fahrenheit), which is good for standard airflow control. They are also resilient to frequent compression, such as when damper blades open and close throughout the day. However, as you noticed, their max temperature doesn’t make the cut for UL’s heat resistance testing.
As we discussed in a previous article, smoke dampers are tested to resist heat of 250 degrees Fahrenheit at the minimum. Smoke dampers are rated 250 degrees or 350 degrees, depending on which form of the heat resistance test they complete. Most smoke dampers from Air Balance have been tested and approved for both 250 and 350 degrees.
You would choose the heat resistance that best meets the needs of the requirement. For smoke dampers, manufacturers will use pure silicone seals dyed orange to distinguish the damper from other types. Silicone seals are resistant to 200 degrees Celsius (392 degrees Fahrenheit). This resilience makes them perfect for smoke dampers.
There is also a slight difference in the material used to make each damper. Control dampers can be made from aluminum or steel, while smoke dampers are only built from steel. Manufacturers will also use steel parts where possible to maximize the damper’s resilience to heat.
It can be difficult to spot the difference between an aluminum damper and a steel damper from a visual check, which is why it’s important to review the damper’s submittal. The submittal will list the materials used for each component of the damper.
Both damper types can receive actuators that open and close the blades.
For control dampers, the actuator you choose will depend on the installation area. For example, older buildings may use a pneumatic system for controlling dampers, which need a matching pneumatic actuator. Most modern projects will use electric actuators for each damper to take advantage of their automation capabilities.
Smoke dampers will need actuators with smoke detectors. The smoke detector will be a separate unit that switches the actuator at the first signs of smoke. Electric actuators provide the means to quickly switch power states once the smoke detector trips. This design ensures the smoke dampers close on detection, thus minimizing the infiltration of smoke through the duct.
You may be thinking that the issue comes down to the smoke detector. Why not add one to a control damper? That way, the damper closes when there is smoke in the duct. A simple fix, right? To demonstrate why that isn’t a good idea, let’s look at the tests involved for each damper type.
Control dampers and smoke dampers undergo different tests to determine their capabilities, although it may not seem that way when it comes to leakage testing. Both damper types can receive leakage testing to find out how much air will pass through the damper when it is fully closed. The individual tests are different.
Manufacturers test smoke dampers in accordance with UL 555S. This includes leakage testing, heat resilience testing, and other intensive situation testing. Control dampers are tested in accordance with AMCA’s standards for dampers, AMCA 500-D. AMCA 500-D outlines leakage testing for control dampers, as well as other tests for other attributes like air performance.
The main difference is the requirements for each damper type. A control damper can be tested separately for air leakage and air performance. The damper receives a certified ratings seal depending on which tests were completed.
These seals signify that the damper completed the tests. They also signify that the data on the submittal was collected in accordance with AMCA standards. The control damper can still perform and meet airflow requirements without these seals.
A smoke damper cannot meet smoke control requirements without completing all the tests outlined in UL 555S. This means that the sample dampers must complete heat resilience testing and leakage testing, one after the other. Only then can it receive approval for use as a smoke damper.
This is the primary difference between control dampers and smoke dampers. A control damper is not tested to the same standard even with a seal for Air Leakage. Smoke dampers are specifically designed and tested for the intense heat of a smoke-filled environment.
It is important to choose the damper that meets the requirements. It may be tempting to substitute for a cheaper option, but that option may not work when it’s needed.
Choose options that meet your requirements, especially with life safety requirements. Smoke and fire control are important in your HVAC system.
Be sure you choose life safety dampers that can perform the task.