Cashins & Associates Blog

Dirty Air Diffuser and Indoor Air Quality

Posted by Mike Cashins on Mon, Nov, 12, 2012 @ 17:11 PM

diffuserOftentimes we will be asked about the fine black dust that is sometimes found on or around the metal blades on an HVAC diffuser. Is this a problem that will impact indoor air quality? The concern of occupants, naturally, is that this is an indication of how dirty the air is that is coming out of the vent. 

Many times, however, this is not the case. When air is pushed out of these diffusers, it creates turbulence, which picks up and deposits dust particles onto the ceiling as well as onto its own metal surface. The swirling air picks up dust particles already in the room and projects them into the ceiling and diffuser. The force of impact allows the particles to stick or embed on the surface.

In other words, it many times is not the air coming out of the diffuser, but objects or activities within the room that produce these fine particles.  Other variables that affect how much particulate clings to ceiling surfaces include relative humidity, diffuser air velocity, static electricity, and temperature.

In short, just because the particulate ends up on the vent, it doesn't mean the air coming out of it is the source.  However, just because it's not coming out of the vent, it doesn't mean that people are unaffected by the particulate.

If there are concerns regarding the buildup of particulate on or around a diffuser, it is recommended that an experienced and qualified Indoor Air Quality consultant be retained. These professionals are experts at identifying potential sources, assessing the quality of the indoor environment, and in making proper recommendations for indoor air quality improvement.

Topics: indoor air quality

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