More Places to Look for Hidden Mold in Buildings - Looking for Mold InspectAPedia® -
Description and photos of oft-forgotten places to look for hidden mold
Guide to finding hidden mold in buildings, under carpets, at ceiling penetrations and air or water leak points
Guide to finding mold hidden on or in furniture
Finding mold in air conditioning systems
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This article provides suggestions for where else to look for mold in buildings - places that are often forgotten but places
that can harbor significant toxic or allergenic mold reservoirs.
The fact that mold is said by some inspectors to be "hidden" in buildings does not mean one cannot find it by careful inspection and testing.
We look for mold in buildings where it is not obvious by using context: where do we see leak stains,
or where do we see building practices most likely to have produced a hidden leak or moisture problem? Ice dam leaks in walls,
hidden plumbing leaks, roof spillage by the foundation, are all common clues that often track to a wet building wall or ceiling cavity and
from there to a hidden mold problem which may need to be addressed.
This procedure helps identify the presence of or locate the probable sources of mold reservoirs in buildings, and helps decide which of these need more
invasive, exhaustive inspection and testing.
Other Places to Look for Hidden Mold Contamination or Mold Growth
There are many places to look for mold growth. Here are a few others that you might not have considered:
Underside of carpets or carpet padding that have been wet - check for moldy or water-stained carpet tack strips;
Previously wet cardboard boxes and their contents;
Ceiling penetrations like 120-V smoke detectors;
Top of poorly-insulated exterior walls; behind wallpaper below windows which had a one-time or recurrent leak.
Furniture: we often find extensive mold on the un-finished side of drawers, tables, game tables, and chairs that have been in a wet or damp environment.
Imported Mold: Sometimes mold is imported into a "dry" building on furnishings or contents that were previously stored in a wet location or in another moldy building.
Building Insulation is often moldy even if it looks clean.
Appliances: Don't forget to clean your refrigerator, including gaskets, coils, and evaporator tray.
Air Conditioning Systems: take a careful look at your window or wall-mounted air conditioner and be sure to make a complete
inspection of central air conditioning system ductwork, registers, and air handlers, as well as any heating air handlers and duct work. Check especially downstream of the air handler on cooling systems since condensation there may promote mold growth.
Have You Found Other Places to look for mold? Send us your own discoveries - your tips may help other people who are bothered by indoor mold but who have
not been able to find its source.
Here are photos of more places to look for hidden mold in buildings
Here we provide a photo tour of mold which was hidden at least from some investigators and occupants, with photo and text tips on spotting problem mold in air conditioning systems, behind and under bath and other cabinets,
mold under and in wall to wall carpeting, mold on stored paper files, file folders, and books, mold on, in, and under furniture, and mold behind wallpaper.
Where to look for hidden mold in air conditioning equipment interiors and in HVAC duct work
Photo of mold inside of a Florida Air Conditioning air handler unit - Mark Cramer, Tampa, FL.
Mold may be found growing on insulation or even on metal surfaces inside of an air handler unit, such as on the blades of the squirrel cage fan in the blower compartment.
Anywhere that house dust and debris are deposited on the surfaces of an HVAC system we may find mold growth - that's because house dust contains lots of skin cells and often other organic debris that can support fungal growth.
But mold growth in an air handler or air duct is more likely where moisture is present at problematic levels, such as where condensate is blowing onto the fan assembly or duct interior when it should be captured and drained away by the condensate drain system.
So also look for mold inside of ductwork or air handler sections that are downstream in the air pathway from the blower assembly itself.
And pay particular attention to air handler equipment or ductwork that has been wet from leaks, condensate leaks, or other moisture sources such as building flooding.
How We Find Hidden mold behind bathroom and other cabinets
Photos of mold behind a bathroom vanity cabinet base - shower water leaked across the bath floor, under the vanity, and into the wall cavity.
This was a small mold cleanup area, less than 10 sq .ft. and suitable for handling by a homeowner or handyman. The second photo shows the extent
of mold after the cabinet was removed.
When we rebuilt this bathroom, since the tile floor slopes slightly down from tub towards the
vanity base, as precautions against future mold growth we sealed all of the new vanity underside surfaces to reduce moisture and thus mold growth,
and we caulked the vanity carefully at the floor level to prevent water from passing below.
Tips for Finding Hidden Mold Below Built-in Bureau Drawers
The previously-hidden toxic black mold (Aspergillus niger) shown in this photograph was found
beneath a built-in bathroom storage drawer - shower water leaked across the bath floor, under the built-in, and into the wall cavity.
I found this incompletely cleaned area during a post-remediation mold clearance inspection and test.
This was a small mold cleanup area, less than 10 sq .ft. and suitable for handling by a homeowner or handyman had there
not already been a costly mold remediation project at this property. In this case the remediator returned to complete
the work.
Failing to simply pull out a drawer to look into the built-in cavity is an indication of superficial workmanship
on a mold cleanup job. Here is a mold test lab photo of Pen/Asp spore chains that we had found in our mold clearance inspection
sample of settled dust taken near this bathroom.
Here is a mold test lab photo of the actual Aspergillus niger colony sample I collected from the pine tongue and groove subflooring
in the moldy area shown above - this is a probable source of the spore chain found in our screening sample.
How to Find Hidden mold below wall to wall carpeting:
Hidden mold in and under wall to wall carpeting is notorious and widespread in areas which have been subject to wet conditions such
as basements or floors on leaky slabs.
The first photo at left shows moldy carpet tack strips which confirms a history of water entry and
makes the carpeting highly suspect of serving as a problem mold reservoir. (We tested the carpeting further using a special vacuum mold test method.)
The second photo shows clean carpet tack strips, indicating that at least since this wall to wall carpeting has been installed there
has been no water below the carpet in this area, and suggesting that the risk of mold in this carpeting is low.
Of course mold may be visible on the surface of carpeting too, such as in this closet.
In this case we suspected that the
visible carpet mold was the "tip of an iceberg" of hidden mold below.
How to Spot Hidden mold on stored papers and files in cabinets:
Paper files and documents and file folders, even stored in metal file cabinets, can become quite moldy when left in a damp
basement. In these photos the file cabinet was never itself wet, but the floor beneath it had been wet several times
leading to extensive mold growth on these law office files.
There are procedures for cleaning and salvaging moldy books
and paper files, but the cost is high, making it appropriate only in special circumstances such as the preservation of works of
art or valuable books or historic papers.
How to Recognize Hidden Mold on and in Furniture:
Upholstered furniture can be quite moldy if it has been exposed to flooding (photos above).
Only in unusually severe circumstances
will upholstered furniture be visibly moldy. Don't forget to look on the underside of couches, tables, and chairs,
especially since the un-finished but hidden surfaces such as raw wood under a table or cabinet more easily
take up moisture and support mold growth.
The condition of the moldy green chair in the photo (left), from a lakefront cottage in Elk Lake Michigan, was pretty obvious
after it had spent a decade in the damp cottage. Moldy furniture like this must either be discarded or stripped to its bare frame
for cleaning before reupholstering.
Remember to use your light (as we describe here and in other articles)
to look along finished wood surfaces as often light colored problem mold is hard to see but may be quite extensive.
How to Find Mold Hidden Behind Wallpaper
Building wallpaper may include problematic molds such as Aspergillus sp. and Stachybotrys in areas subject to leaks
such as below the window in the condominium in New Jersey, or in bathrooms where wallpaper was applied.
We suspected mold and convinced our daughter to peel down the wallpaper below this window because she had told us that there had
been a history of wind-blown rain leaks at this particular opening.
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Additional technical contributors & reference sources for this article are listed below.
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06 and 04/2008
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
Allergen Tests in Buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
Rodent control issues, including dander, fecal, and urine contamination of Buildings and Building insulation are discussed at our
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon)
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold
Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold
cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.
Ozone Warnings - Use of Ozone as a "mold"
remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the
areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic
bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details
see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings,
and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating
the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing
rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some
help from a licensed pest control expert.
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