Additional specifications and description
This device may be found under a few different names but is typically referred to as a circular backdraft damper or a round non-return damper. Its main purpose is to only allow the flow of air in one direction, which is required in a lot of applications found in domestic and industrial ventilation/HVAC systems. The valve component of the damper is comprised of half circle-shaped blades with a spring-loaded butterfly mechanism. In order for air to flow in the desired direction, all that is needed is a slight pressure difference, and the one-way valve will open and allow air to flow past the blades. However, if there is higher pressure in the opposite direction i.e. a backdraft, then the blades will be pressed firmly against the foam seal, thus blocking any air from flowing through the damper. The foam seal not only ensures good air tightness but also reduces any unwanted noise or rattle coming from the damper's mechanism, especially if there are gusts of wind or other sudden pressure changes.
Backdraft dampers in homes are mainly used to prevent fumes and smoke from a kitchen extractor from flowing back in. When used in bathrooms, laundry rooms, and wet rooms, the damper stops any moist air that is exhausted outside from being sucked back in and helps with the ventilation of these typically damp rooms. In an industrial environment, it is even more crucial to use non-return dampers as toxic vapours or fumes can be released during production, or even when materials sit in storage. These toxic compounds have to be extracted by the ventilation system, without allowing any contaminated air to flow back in.
Therefore, these dampers are a key component in maintaining indoor air quality and creating an accurate flow of air. Besides air quality non-return dampers improve energy efficiency as well, for example in the winter they prevent cold air from entering through an exhaust ventilation duct, and inversely they stop hot air from entering an air-conditioned room or building in the summer. Another benefit is that when installed in conjunction with an axial fan, the non-return damper prevents the outside air pressure or gusts of wind from rotating the blades backward while the fan is off. Lastly, though this is not their intended use, non-return dampers will also block debris from entering the duct and potentially causing damage.
Construction and installation method:
This round non-return damper is designed to be mounted in between two circular or spiro ducts and can function in both horizontal and vertical orientations thanks to its spring-loaded operation. Models without an EPDM gasket require the use of sealant to prevent air leaks. The metal construction makes this ventilation piece very robust, corrosion-resistant, and long-lasting, even in harsh environments. Once installed the non-return damper is practically maintenance-free.