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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. Also see MOLD GROWTH on SURFACES for an index of what mold genera/species are frequently found on various building surfaces and materials.

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MOLDY CARPETING - in buildings, how to recognize allergenic or mold contaminated carpets and rugs

While you may see mold on carpeting in unusually severe cases, carpet, especially wall-to-wall carpeting can be a reservoir for hidden mold, mite fecal, pet dander, rodent dander, fecals, and dust, bacteria, and other allergens, pathogens, and irritants even though you cannot see anything suspicious on the carpet. Here are some warning signs that carpeting may be an IAQ problem source in a building:

• Carpets which are visibly moldy such as in the photo above - these need to be discarded.
• Carpets that have been wet such as by basement water entry, a plumbing leak, roof leak, sewer line backup. If wall-to-wall carpeting has been wet it probably should be removed and disposed-of. There are services which will remove wet carpeting and clean it for reinstallation. If wet carpeting is removed and cleaned and dried in 24-48 hours it might have a chance - I'm waiting for more field test data before I recommend this approach. If carpet was wet and stayed wet it's history. Area rugs can often be professionally cleaned and salvaged.
• Carpets over wet padding or carpets, carpet padding, or carpet tack strips which are water stained or moldy indicating that water or condensation has been present below the carpet. The photo shown here is an example of a moldy carpet tack strip which offers a clue of a limited area of water entry in a basement although no staining was visible on the exposed top of the carpet.
  
  Notice the small brown stain spots on the back side of this carpet? These are rust marks from the carpet tack strip - another indicator of wet conditions below this carpeting.
• Carpets in basements or located on floors below grade such as in split level homes, particularly in areas where there are periods of high humidity or wide temperature swings in a building likely to produce condensation.
• Carpets exposed to high pet traffic are likely to have a high level of animal dander and, depending on the building humidity history, almost always have a high level of mite fecals and other allergens - this is not a mold problem but is likely to be an IAQ problem especially for people who are asthmatic or allergic to pets.
  
  I have tested carpets before and after home vacuuming, home HEPA vacuuming, and professional dry and wet process cleaning. None of these methods can completely clean a carpet, though they might temporarily reduce the level of particles in the very top of the carpet nap.
• Carpet odors: carpeting that smells can be caused by a wide range of problems. See ODORS & SMELLS DIAGNOSIS & CURE
• Carpet stains: can also be caused by a wide range of sources, some of which are harmless, others may diagnose other building problems such as a heating system that is not working properly, or building air leaks. See CARPET STAIN DIAGNOSIS.

How to Look for Hidden mold in or underneath wall to wall carpeting and carpet padding

Advice for Testing Indoor Carpeting for Mold Contamination

If carpeting has been wet and was not dried within about 24 hours after that event, it is likely to be moldy. if carpeting smells or looks moldy it also will almost certainly need to be replaced. But what if we don't know a carpet's history, we don't see mold on the carpet nor on it's underside, but we need to test the carpeting for mold?

Details of our advice on testing carpeting for mold or other contaminants can be read at CARPET TEST GUIDE.

In addition to taking a careful case history of the leak exposure to which carpeting has been exposed, and in addition to making a thorough olfactory (subjective smell test) and visual (by eye) inspection, we on occasion test carpeting using a vacuum method, combining a vacuum pump with a sampling cassette.

Selection of the area of carpet to be tested is important: choose the most-suspect area of carpeting such as where leaks or water are likely to have been present or where there may have been cross-contamination from mold remediation in other areas of the building.

We advise against use of tape samples of a carpet upper surface to screen carpeting for mold since there is a significant risk that such methods will fail to detect problem mold that is in the carpet but not on its uppermost surface. This condition occurs, for example, when moldy carpeting has been HEPA vacuumed or cleaned.

However, if there is mold already visible on a carpet (such as is shown in the next section of this article) it may be appropriate to collect a surface sample using tape in order to identify the type of mold present when that data is needed for medical or post-remediation clearance test purposes.

How to Recognize Mold Visible on Exposed Carpeting Surfaces

Mold visible on carpeting surfaces: 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. Details about types of stains on carpeting, their cause, significance, and cure, are at CARPET STAIN DIAGNOSIS.

Daniel Friedman is a mold/indoor air quality investigator and home inspector as well as a professional writer in Poughkeepsie, New York. He is a member of the American Industrial Hygiene Association and the American Society of Home Inspectors. He presently chairs ASHI's national Standards of Practice Committee and has led ASHI's Education and Technical Committees as well as serving on ASHI's Exam, and Ethics/Professional Practices Committees. His poetry has appeared in Emphasis, a national publication of MENSA, and his non-fiction articles and essays have appeared in The Journal of Light Construction, the Old House Journal, The ASHI Technical Journal, Progressive Builder and New Shelter. His news reporting and photography have appeared in the Journal of Light Construction, and in various newspapers including the New York Times, Richmond Times Dispatch, Richmond News Leader, and the Poughkeepsie Journal.

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More Information on Building Diagnostic Inspections and Repairs

• 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.
• Basketball Mold Syndrome - BBMS- sudden attention to old clues in buildings makes them seem brand new to some observers
• 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

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