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Legionella contamination in air conditioners & heat pumps:
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.
Cleaning suggestions for A/C System Condensate Systems
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?
Should we be putting bromide or chlorine tablets in our condensate trays to keep bacteria from growing?
If we should be, then do we need to alternate bromide with chlorine on some type of frequency to prevent development of resistant bacteria?
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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
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.
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Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
home inspection educator.
http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html is OSHA"s technical manual re Legionnaire's disease US EPA Safe Drinking Water Hotline: 800-426-4791
"Legionella in NY - How to Conduct a Legionella Risk Assessment", Mark Hodgson, LSC, Naperville IL & Diane Miskowski, MPH, EMSL Analytical, Inc., Westmont NY, Crown Plaza, White Plains, 8 May 2007. Course description:
"Guidelines for the control of Legionella in critical care hospitals in New York have been in place for two years. In October 2006, these guidelines
were extended to include nursing homes and long term care facilities. Join us for this 8 hour seminar to learn all you need to know to conduct
a Legionella health risk assessment, control it in your facility, and remediate it. This course will describe the ecology of the [Legionella] organism,
the epidemiology of the disease [Legionnaire's disease], a discussion of some recent outbreaks, and the proper sampling methods and analysis
of the bacteria. A significant amount of time will be spent discussing how to actually perform a Legionella risk assessment, and an
overview of cooling towers and potable water system design and how that contributes to growth of the [Legionella] organism. Discussion
will include where Legionella can be found in the engineered environment, and the use of biocides and other controls."
Thanks to Craig Balchunas, AHI Accurate, LLC., a home inspection firm in Hyde Park, NY. - (800) 360-3998
"Legionella", a public information poster provided free by LA Testing, an California environmental testing lab - www.LATesting.com.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones