Most of the reactive IAQ projects we work on are in response to someone complaining about IAQ. When that occurs (in addition to speaking with the complainant) we look at air handler units for the complaint area. We have learned over the years, that a failure in one or another aspect of AHU maintenance, can often generate the contaminants causing problems.
Early on in my career, I stuck my head into a poorly maintained air handler unit to do an inspection. My flashlight showed me a colorful and fuzzy indoor environment … and my sinuses told me to get out! Too late! I have never known what I breathed, but I learned a good lesson. (Always let someone else look into the AHU first!)
Today, to complete our review of the air handlers, we turn the unit off and open access doors. Some of the components we look at include the following:
Fan assembly – while the fan housing can be clean, often times the fan blades will not be. On the other hand, if either the blades or the housing are dirty, they can be a source of excess particles in the indoor air.
Coil surfaces – Dust and dirt that make it past the filter system will often become impacted on the coil. In many cases, this is seen as a black or slimy discoloration on the surface of the coil. This is often a bacteria that should not be there.
Drain pans – Condensate drain pans are also an occasional concern. If the pans are not draining properly, water will sit in one spot and stagnate. This then allows bacteria to grow. Making sure the pans are flushed out regularly and that antimicrobial tablets are placed in the pan, can prevent this from occurring.
Internal Insulation – Insulation near the evaporator coil can also be a serious concern. This is because it can become wet when water is thrown off of the coil. Wet insulation can grow mold, so we always look for discoloration or evidence of moisture on the internal insulation surfaces.
There are other issues that can occur in air handler units depending on the design of the unit, but one benchmark is constant. The regular maintenance of air handler units can prevent many of these concerns from occurring, and will certainly ensure that they are not the source of IAQ problems when occupants complain.
More soon!