How to find light-colored, hard-to-see mold in buildings

How to find light-colored, hard-to-see mold growth on building surfaces
HIDDEN MOLD, HOW TO FIND where & how to look for hidden mold contamination in buildings
Questions & answers about how to find light colored, hard to see mold contamination in buildings
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This article explains how to find and test for light or hard-to-see mold growth on building surfaces. The photo at page top shows a hard-to-see light-colored (possibly toxic) mold on the surface of an interior door. It is easy to miss large areas of light colored mold like this unless a careful inspection is made and careful use of light is applied.

Too many "mold inspectors" are quick to test the obvious "black molds" found on building surfaces while they may fail to find and identify possibly more harmful mold species simply because they ignored the light-colored mold growth. This document describes how to find mold and test for mold in buildings, including how and where to collect mold samples using adhesive tape - an easy, inexpensive, low-tech but very effective mold testing method.

Also see FIND MOLD in BUILDINGS, HOW TO and see MOLD GROWTH on SURFACES for an index of what mold genera/species are frequently found on various building surfaces and materials, and see Mold Related Illness: Index of Symptoms and finally, for an atlas of building molds and for more microphotographs of building mold samples observed in our laboratory, see Mold Atlas of Indoor Clinical Mold, Pathogens, Allergens & Other Indoor Particles. And MOLD BY MICROSCOPE shows what mold looks like under the microscope.

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.

Spotting light colored, hard to see, toxic molds indoors

Other mold species are light in color or nearly invisible when growing on an interior surface unless you look carefully. This desk sat in a wet basement for only two months yet it was rapidly covered with a toxic mold, Aspergillus niger. Aspergillus molds indoors can be difficult to see.

A. niger spores are tiny and are easily made airborne by the smallest disturbance. The basement housing this moldy chest had Aspergillus levels in air enormously higher than the outdoor sample.

Aspergillus on furniture

Photo of moldy TV stand in an upper floor den of a house subject to high moisture conditions

We find as much or more Penicillium/Aspergillus in houses than Stachybotrys, but these light green, gray or tan mold colonies are more difficult to see if you don't know how to look.

To check more carefully and thus more successfully for mold, shine your flashlight along the wall surface in an area that has been damp or wet.

Don't shine it right at the wall or you won't see much. Look where things have been wet or damp, regardless of whether it was a single event (washer flood) or one that happens at every rainstorm.

This photo of three different mold genera/species growing on a laundry room wall demonstrate that a lot depends on just where you collect your tape sample when identifying mold in buildings

Keep in mind that different molds like different moisture, temperature, and food.

One reason that S. chartarum has been "over-reported" as a problem in some studies is that the field "experts" didn't look for lighter molds, and maybe they didn't even carry a flash light. The photo here shows three tape samples being taken from different heights on a laundry room wall.

Three different mold species were found, one in each area. Only the lowest black mold was obvious.

In this wall test of three molds which were growing quite close together, I've marked each tape sample so that you can see where it was on the wall. #1 =Stachybotrys chartarum, #2 = Ulocladium chartarum, #3 = Aspergillus sp.. - it is this third mold which, in a larger quantity, would be airborne and more likely to bother building occupants. Yet nearly 100% of home owners and 80% of industrial hygienists and 90% of home inspectors who send mold samples to our lab are going to tape-sample only the "dark mold" on this wall.

Why are there three different genera/species on this drywall? Most likely because each of them prefers a different moisture level in the paper which they're digesting. I can generally track the mold genera up the wall as a function of the moisture gradients in the wall. When a wall has been wet because of wet floor conditions, the drywall and in-cavity wall insulation will be wettest at the wall bottom.

Be sure to review our notes above on use of lighting at Use of a flashlight to find mold since if you don't know exactly how to use a flashlight, as simple as it seems, you're not going to find important light-colored molds in buildings.

Where to Look for Hidden Mold - an Example Using Air Conditioner Air Handling Equipment interiors

Photo of light-colored mold inside of a Florida air conditioning air handler unit - Mark Cramer, Tampa

See Other Places to Look for Hidden Mold for details of this and other places to look for hidden mold in buildings.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Mold Safety Warnings for Do-It-Yourself'ers Planning to Inspect for or Clean Up Mold Contamination

Warning notice

Guidelines defining what's a "large amount" of mold and what's reasonable for a homeowner to handle have been published by several states including New York and California.

People who are allergic, asthmatic, infant, elderly, immune-impaired, etc., should not disturb mold and should not be in the area where mold remediation is being performed. Consult with your doctor, health department or other professional before tackling this job yourself.

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.

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.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
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.
Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
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
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

Mold Contamination Testing, Cleanup, Prevention: references & products

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Aerobiology, Building Science, Microscopy, & Laboratory References, an extensive technical bibliography
Allergens: what they look like in buildings
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) - The Atlas of Clinical Fungi is also available on CD ROM
Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
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?
Clinical Mold References - Detailed bibliography of mold reference texts
"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
"Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Fiberglass: Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
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.
Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
Looking for Mold Procedure: what mold is often found where in buildings - simple technical presentation
Meruliporia: the house eating fungus or "poria"
Mold Action Guide: Step-by-Step Instructions, What to do about mold, mildew, and other indoor allergens
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE Photos of what mold looks like in buildings
MOLD APPEARANCE - STUFF THAT IS NOT MOLD Photos of NOT-mold material that is sometimes mistaken for mold
MOLD ATLAS & PARTICLES INDEX, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
MOLD BY MICROSCOPE Mold under the microscope - photo identification of the most common indoor molds found in buildings
Mold FAQs Answers to Most Questions about Indoor Mold, Mold Related Illness, Mold Cleanup, Mold Prevention
US EPA: Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab or to any mold lab you wish
Most Common Indoor Molds Found in Buildings, A Table of
Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

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.

Fiberglass building insulation and HVAC duct work insulation hazards
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Other environmental risks: Asbestos, carbon monoxide, electromagnetic fields, environmental illness, fiberglass, MCS - multiple chemical sensitivity, toxic gases, etc
Indoor Gas Sampling Plan for Residential Buildings lists a number of toxic indoor gases which we test for, depending on the building complaint and building conditions
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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