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The fact that mold is "hidden" in buildings, such as inside a wall cavity, does not mean one cannot find where the problem mold is located. We look by 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. Also see MOLD GROWTH on SURFACES for an index of what mold genera/species are frequently found on various building surfaces and materials.

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. 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.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Spotting Hard-to-See Mold on Paneling in the Living Area

USING LIGHT - Using proper lighting to see important mold contamination in buildings

How and where you shine light is of crucial importance when looking for mold in buildings. Light-colored mold such as some members of the Aspergillus sp. and Penicillium sp. groups are often the dominant problem-mold in buildings but these offenders are often missed by a casual inspection because they can be hard to see on surfaces.

You need a bright flashlight and you need to know how to use it. Shine the light along the surface being examined, not straight at it. As you'll see in the mold photographs below, using your light carefully can make a big difference in what mold you find and where you find it. Just looking for "black mold" risks missing the important mold in a building.

Light colored toxic mold on paneling is not visible because light is being shone directly onto the wainscot wood paneling surface.

Now try shining a light along the surface - this easily shows the white mold colony.

The point of these illustrations is to demonstrate that "hidden mold", like the purloined letter, may in fact be hiding in plain view - you just don't know how to see it.

Is Toxic Black Mold the Only Mold To Worry About in Buildings?

In short, no, absolutely not. Here are some details:

Recent news articles have made some people terrified at the mere mention of "toxic black mold" such as "Stachybotrys chartarum." Actually it is common to find Stachybotrys chartarum in small amounts in houses where there has been prolonged leakage or water entry. It's a toxic mold that should be removed.

But don't assume that anything and everything black on a building wall is a highly toxic mold. Some black stuff is not mold at all. See STUFF THAT IS NOT MOLD for details of black stains or debris on walls that have no mold hazard whatsoever.

Other common mold species look black but may be of low or no toxicity. For example, Chaetomium globosum has been reported to be allergenic rather than toxic. Cladosporium sphaerospermum is often found growing indoors on bathroom tile or refrigerator gaskets. It's a member of the most common mold family, Cladosporium, the "universal fungus." It can look pretty "black" on some surfaces.

Still other black molds found in buildings are completely harmless. See   Recognize Cosmetic Mold and  Recognize Harmless Black Mold for details about these cosmetic molds and easy ways to spot some of them with no testing whatsoever. Just common sense can tell you that some molds have been on a surface since the time of construction.

Finally, there are plenty of highly toxic or highly allergenic or irritating molds found in buildings that are not black or even dark, especially including most members of the Aspergillus sp. and Penicillium sp. families. See  Light colored toxic molds for details.

Is it Possible to Identify a Mold Just by Looking At It On a Building Surface?

Can you tell what genera or species a mold is that's growing on a surface just by the naked eye?

No. Though I've inspected and tested so many molds on so many surfaces that like a bird watcher, I know what's likely to be present in a given habitat. (Refrigerator gasket mold is usually a Cladosporium, often C. sphaerospermum and mold growing on window muntins will be a genera/species tolerant of UV light. A normal person can't do this, though a mold investigator and a few mold remediators with plenty of experience can make a reasonable guess. (Such guesses are not always right.)

You cannot determine the mold genera and species just by looking at mold on the wall. Skip those do-it-yourself mold test kits that rely on culture or settlement plates. The methods the kits use are fundamentally inaccurate and in a few cases so are their laboratories. (90% of mold species will not grow on culture media.)

For small mold problems, spend your money on some soap and water instead.

For larger mold contamination problems hire an expert to survey your home, or send your own mold sample to a competent testing laboratory. The services of an experienced mycologist or aerobiologist are necessary to know what you've got. (C)DJF Copyright protection trap.(C)Daniel Friedman

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MOLD INFORMATION CENTER
MOLD DETECTION & INSPECTION
HOW TO LOOK FOR MOLD
  CHOOSE SAMPLE POINT
  SAMPLING DRYWALL
  SAMPLING MISTAKES
  USE A FLASHLIGHT
WHAT MOLD LOOKS LIKE
ATTIC MOLD
BASEMENT MOLD
BASEMENT MOLD WATER IMPACT
CARPET TEST GUIDE
CAT DANDER
CRAWLSPACE MOLD
DRYWALL MOLD
HIDDEN MOLD, HOW TO FIND
  Photo Guide to Finding Hidden Mold
  Hidden Mold Behind Paneling
  Hidden Mold Between Framing & Sheathing
  Hidden Mold in Flooring & Subflooring
  Hidden Mold in Wall Cavities
  Spotting Hard-to-See Mold
  Use of a flashlight to find mold
  Wall test cuts to spot hidden mold
  Light colored toxic molds
  Moisture Gradients and Mold
  Other Places to Look for Hidden Mold
INSULATION MOLD
ITCHY FABRICS
MOLD BY MICROSCOPE
MOLD on DIRT FLOORS
MOLD on or in CARPETS
STAINS on Indoor Surfaces: PHOTO GUIDE
STUFF THAT IS NOT MOLD
  HARMLESS INDOOR PARTICLES
  THERMAL TRACKING STAINS
USING LIGHT TO FIND MOLD

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Books, Complete List of Environmental Inspection, Diagnosis, Cleanup, Air Quality & Design, Inspection, Repair Books at the InspectAPedia Bookstore
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Books, Complete List of Environmental Inspection, Diagnosis, Cleanup, Air Quality & Design, Inspection, Repair Books at the InspectAPedia Bookstore
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• ...

More Information on Building Diagnostic Inspections and Repairs

Mold and Allergen Recognition and Identification - Not All "Black Mold" is Harmful; Some Suspect Stuff is Not Mold

• How to Find and Test For Mold in Buildings - Looking for Mold - A 'how to' photo and text primer on finding and testing for mold in buildings
• Recognizing Mold: What mold looks like mold identification photos to help identify mold - choosing what to sample in buildings
• 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
• Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
• Mold Action Guide: an easy step by step outline of what to do about mold
• How to find mold without hiring anyone, for do-it-yourself'ers
• Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
• Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab
• How to find a mold inspector or test consultant: Directory of IAQ,Sick Building, Mold Allergen Testing, Building Investigation Service Providers
• Meruliporia: the house eating fungus or "poria"
• Mold Investigation Tips for Home Inspectors how to find mold, where to look, what is likely to be important. Advice to building inspectors intending to inspect or test for toxic or problematic mold indoors, mold inspection methods, and mold test methods which are valid or invalid
• Mold Risk Levels in Buildings Based on Visual Inspection - simple visual clues help decide on action
• Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
• Frequently Asked Questions About Mold -- check this FAQ list & IAQ Site Map to see if you can find a quick answer to your mold concern
• When to hire a professional to inspect for toxic mold or other allergens
• Contact Us to arrange mold/IAQ building on site inspection and testing.

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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

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

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