No one likes to see visible evidence of a dirty HVAC system in their office. It conjures images of magnified dust mites, pathogens, and contaminants lurking in the air ducts and being expelled into the workspace, leaving employees wanting to hold their breath. Supply diffusers and return grilles are usually the most visible element of an office HVAC system, and when they're dirty, building occupants rightly question the cleanliness of the associated ducts and air handlers and by extension, the air they breathe 8 hours a day.
Return grilles and supply diffusers work together in harmony with the HVAC (Heating, Cooling, and Air Conditioning) system to distribute heated or cooled air throughout a commercial building. Air is pulled through the return grates into the system, then heated or cooled in the air handler and returned via the ductwork to the indoor space through the supply diffusers. Supply diffusers function to diffuse or spread out the air into the workspace in a controlled manner rather than blasting it out just beneath the opening in one strong current. Both return grilles and supply diffusers are usually located in the ceiling, and often above desktops.
As air moves through any HVAC system, it picks up dust and debris over time, which recirculates through the system and collects in certain auspicious places. One of these places tends to be the back of supply diffusers. As air blows through them, small amounts of dust are loosened and cling to the front of the diffuser, or are blown into the air or onto desks. It's at this point that the office manager or maintenance supervisor usually calls in a commercial air duct cleaning company, either because they're aware that dirty diffusers and grilles signal a need for cleaning the ducts overall, or because employees are complaining of dust being blown onto their desks (or in cases of fiberglass interior-insulated ducts—black specks of sloughed-off insulation).
Of course, the cleaning of return grilles and supply diffusers is only one step in the process of HVAC system cleaning as a whole, but it is an essential one, because any dirt left in these areas will still be blown into the workspace even if the ducts are clean, but also, because having clean grilles and diffusers instills confidence in the overall cleanliness of the HVAC system.
Most grilles and diffusers can be easily removed for cleaning, which would be the preferred method. (The vent openings are then taped over so that suction is not diminished during the duct cleaning process.) Once they are removed, they're transported outside and washed thoroughly with a degreaser, such as Simple Green, or in tougher cases, Zep, diluted and applied with a Hudson sprayer. They can then be rinsed off with a garden hose and left outside to dry until the duct cleaning is complete.
In cases where the supply diffusers are welded into place, an alternative cleaning method is to first use a dry vacuum on them, followed by hand-wiping with a cloth and degreaser, with the technician reaching his hand behind each of the louvers to ensure its cleanliness.
Often the ceiling tiles in close proximity to supply diffusers also dirty over time from dust expelled. These can be carefully vacuumed to restore them to cleanliness in most cases. Those dirty with grease or other stubborn substances may need to be replaced.
Once the air duct cleaning process is complete and the diffusers and grilles are cleaned and put back in place, the indoor workspace will be observably cleaner, and employees can have confidence that their 8 hours spent in the office, however drudgy or exhilarating, will not be spent breathing dirty air.
Wanna dig deeper? Our commercial air duct cleaning page contains detailed descriptions, before and after photos, and videos of our commercial duct cleaning processes.
Many thanks to our commercial project manager Ben S for lending his expertise to this article.