An Assessment of Aspergillis Fungi Bypass for a Small Commercial HVAC Unit
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Aspergillus is a commonly found fungus in both indoor and outdoor environments. A common, not so harmful fungi for most people, this fungus can lead to aspergillosis in persons with suppressed immunological systems. This is most likely to occur in a hospital setting with patients of differing levels of immuno-compromised status. Aspergillosis is an upper respiratory infection that is similar to other respiratory diseases such as pneumonia. Once the fungus has invaded the lungs, it can easily spread to other parts of the body. Modern healthcare facilities feature the use of air conditioning systems with filters that capture Aspergillus spores before they can be re-distributed to the building through the system ductwork. In this study, air sampling was performed at the inlet (return air) and outlet (supply) grilles of a small, commercial air conditioning unit serving a university classroom/office building. The difference in Aspergillus counts between inlet and outlet of that unit were sampled over a period of two months. Results showed a consistent pattern of a capture of about 40% of the Aspergillus spores entering the unit filter. This also means that about 40% of the Aspergillus spores were bypassing or passing through the air conditioning filter system and being redistributed into the air of the building. These results, when extrapolated to a healthcare facility setting, demonstrate the importance of proper selection, seating/sealing, and maintenance of this important element of the air conditioning system.
Khapuwala, Smit (2018). An Assessment of Aspergillis Fungi Bypass for a Small Commercial HVAC Unit. Master's thesis, Texas A & M University. Available electronically from