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MOLD in AIR HANDLERS & DUCT WORK
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REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
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WATER COOLED AIR CONDITIONERS
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This article explains cause, hazards, & prevention of Legionella bacteria contamination in air conditioners, how to clean air conditioning systems, Legionnaire's disease prevention & cleaning suggestions for air conditioning equipment and condensate trays, including condensate piping, traps, drains, condensate pumps, and concerns for mold, Legionella bacteria, and other hazards associated with air conditioning systems, cooling towers, and evaporative coolers.
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Here we discuss cleaning procedures for HVAC equipment in order to prevent Legionella bacteria formation or to remove it if present, a key step in preventing Legionnaires' disease.
Should we disinfect cooling system equipment or condensate trays to prevent Legionella or other bacterial growth?
If we should be, then do we need to alternate bromide with chlorine on some type of frequency to prevent development of resistant bacteria?
[Click to enlarge any image]
We're discussing condensate trays from mechanical equipment like heat pumps, fan coil units and air handlers with AC coils.
These pieces of equipment have condensate trays which are then drained through a small pipe, usually clear, but not always, with a trap in it, to a drain.
These condensate trays have some standing water in them when the AC is functioning. Should these condensate trays be treated with an algaecide of some sort?
There are risks beyond mold and algae, in particular Legionella bacteria (legionnaire's disease) which can have an alarmingly high mortality rate, and also potential hazard sources such as biofilms that can include other bacterial and maybe other pathogens.
However the risk of formation of problem levels of mold, bacteria, or other pathogen is probably not the same across all buildings nor types of equipment, and much of the risk may depend on installation and maintenance details at individual installations.
Particularly in climates with a high humidity and a heavy cooling load, and depending on details of the design and installation of the air handler unit and duct work, there is risk of blowing pathogen-contaminated water droplets downstream inside the air conditioning duct work and thus exposing building occupants.
With rooftop-mounted cooling units such as cooling towers using water, conditions may be still more attractive for growth of pathogens and there is some risk of movement of pathogens out of the cooling equipment to people located nearby and downwind from the equipment, even if they are outside the building which the equipment actually serves.
While I am not expert on this topic I have collected and provide here some key information and opinions to help sort out these questions. Use the links listed at the "More Reading" links at the bottom of this article to read additional details on this topic including recommended cleaning procedures and details of the Legionella hazard in air conditioning systems, humidifiers, etc.
The health hazards associated with Legionella and other biological contaminants in HVAC systems are at Legionella sp. Health Concerns.
Also see HOT WATER ANTI-SCALD REGULATIONS where we discuss methods for preventing Legionella formation in water heating equipment.
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