This article series addresses just about every common source of contaminants in heating & cooling duct systems, such as sources of bacteria, dust, fiberglass, mold or odors that appear to originate in or be transported by the buildings air duct system.
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Below is an alphabetical list of common air duct contaminants and contamination sources or duct test & inspection methods.
Following our list of duct contaminant diagnostic articles we illustrate and discuss some common examples of air duct contamination, dust, dirt and debris - or perhaps of more concern, pathogens.
Watch out: don't panic if you see dust inside the HVAC system, or exposed fiberglass. Both of these conditions are common and do not necessarily mean that the air ducts are unsanitary or unsafe.
However if you see signs of water, visible mold, flooding, rodents, or if you see that the duct interior has been damaged like the fiberglass-lined duct shown a the top of this page (DUCT DAMAGE, MECHANICAL) there may indeed be a problem that needs to be addressed.
At above right we illustrate an air duct that was routed below the first floor of a buildnng and accessible from the basement.
A look inside showed us that there had been of a history of flooding - dirt and mud on the duct bottom - meaning that floodwaters had at one time filled the basement.
Watch out: area flooding may contaminate ductwork with sewage or other pathogens even for above-ground-level HVAC ducts, while a building sewage backup can certainly contaminate ductwork run in floors or in a floor slab.
At above left we illustrate an abandoned HVAC duct in a concrete floor slab. It's quite apparent that the area remains wet along with an added risk of contaminants of sewage, pesticides, rodents, insects, or anything that spilled on the floor in this area.
Our HVAC duct interior photograph at above right shows a melange of contamination by animal hair, dog food, and rodent droppings. Mice were eating the dog food that spilled into this return air duct opening at a floor register. The potential pathogens invovled here include at least bacteria, possibly hantavirus and mold.
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