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The photo above shows several colors of mold on a drywall surface. Still more mold may be present but still lighter in color and harder to see. Each of these may be a different mold genera or species. Which molds that we see on a building surface should be sampled? We explain the answers here. At Wall test cuts to spot hidden mold we discuss finding mold on the wall cavity side of drywall. Also see MOLD RESISTANT DRYWALL for a discussion of that product type as well as a list of drywall or gypsum board industry standards and drywall product MSDS sheets.

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.

This chapter is part of a 'how to' photo and text primer on finding and testing for mold in buildings using simple clear adhesive tape on suspect or visibly moldy surfaces.

© Copyright 2009 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.

SAMPLING Building DRYWALL Gypsum Board, "Sheetrock" and other Building Surfaces for Mold Using Clear Adhesive Tape

As I've explained in various articles and at our instructions for collecting and mailing a tape sample to our lab, different mold genera/species will be found growing on the same or nearby sections of drywall on a building surface, depending on several variables.

If the largest contiguous mold area in a building is trivial in amount, say 1 sq .ft., we would not test it unless we thought that the mold we see is representative of a larger mold problem I cannot see. Small areas of mold should simply be removed.

For larger areas of mold (certainly if more than 30 sq .ft. of area is moldy or if mold is growing on many surfaces in a building), you are looking for the dominant species present and particularly allergenic or toxic species present in the environment.

How to Decide Where to Sample for Mold and How Many Mold Samples To Collect

Collect one mold tape sample per location; do not use the same tape to sample from multiple locations.

• Choose a representative sample spot: select a representative spot of mold growth on a surface such as a wall, cabinet, ceiling or floor.
  
  This means that if you see what appears to be a single coating of mold-suspect growth on a surface, all rather consistent by color, texture, and what it's growing-on, you need only one sample of that material. Variations in appearance or texture or growth surface or mold growing in different building areas or floors are reasons to sample more than one thing.
  
  In our photo (above left) of severe indoor mold contamination in a home, many different mold genera/species were present on the drywall (sample by color or texture) as well as still other genera/species that varied by growth surface, type of wood, painted surfaces, other materials.
  
• Color: Sample molds of different colors: black, white, green, red, gray, brown, yellow, pink - are often (not always) different species.
• Texture: Sample molds of different textures: hard lumpy big grainy versus fuzzy and easily blowing into the air - are often (not always) different species.
• Growth Surface: Sample molds growing on different building materials. This is quite important. Completely different mold genera and species may be found growing in the same building on different growth substrates: drywall room side, drywall cavity side, plywood sheathing, wood stud or joist framing, painted surfaces, exposed fiberglass insulation kraft paper vapor barrier - are often (not always) different species. Even on the same growth surface (drywall for example) different mold species appear at different locations according to variations in moisture level - explained just below)
• Building area: basement, crawl space, living area, and attic all have different moisture conditions, often different building materials, different patterns of air movement and exposure. The "green mold" found on wood subflooring visible overhead from inspection in the basement is very often a completely different genera and species from the "green mold" found on the roof sheathing in the attic of the same building.
• Representative dust samples: we will sometimes screen areas where there is no visible mold by collecting settled dust particles from a horizontal surface. If you are going to collect a single dust screening sample, collect it either from the area of which you are most suspicious (a flooding basement), or from the area where building occupants spend the most time (perhaps a bedroom or family room).
  
• Variations in moisture gradient in the drywall - so if a floor was flooded, water-loving molds grow closest to the floor (such as highly-visible black molds like Stachybotrys chartarum), while molds liking the drywall to be a little less wet grow a little higher (such as Cladosporium sp., Cladosporium sphaerospermum, Cladosporium cladosporioides, Ulocladium chartarum), and molds liking the drywall to be still less wet grow higher still on a vertical wall (such as Aspergillus sp., Aspergillus glaucus, Aspergillus flavus, Penicillium sp., etc.). Therefore where the tape sample is collected can make a big difference in what you find.



In the first photo of moldy drywall, three completely different mold genera and species were within a few inches of one another at different heights on this laundry room wall.

This condition often occurs, but the different genera may be as close as inter-mixed and even overlapping in the same area, to growing several feet apart on the same wall, to growing in the same building but on different materials on different surfaces.

In this case, tape sample #1, the bottom mold, was Stachybotrys chartarum, tape sample #2, the middle mold, was Cladosporium sphaerospermum, and the top tape sample, #3, was Aspergillus flavus. Of these three, the Aspergillus is the easily-airborne toxic spore which is more likely to be a problem in the building if it is present in sufficient quantity.

How to Prepare & Save Mold Tape Samples for Mailing to a Mold Test Laboratory



In this photo detail you'll see that using a new and clean zip-lok™ bag, we placed several surface tape samples on the same bag. If you can't assure that the bag surface is clean between tape sampling, use a new bag for each sample.

• Interruptions in the moisture gradient absorption path: for example at a wet floor which soaks the bottom of drywall, moisture wicks up into the drywall material. But moisture wicking may be reduced suddenly at a horizontal drywall joint, resulting in easily-visible borders or lines in fungal growth.
  
  
• Exact pathway of water on a surface or in a building cavity: so tracing the exact water path through a ceiling or wall cavity is very important.

Are you collecting too many mold test samples?

There are nearly always multiple mold species present in any environment where mold producing conditions are present.

We sample surfaces likely to host different molds, focusing on surfaces which appear to represent mold or mold-suspect material growing over large areas in the building. Don't collect and send 50 samples. If you find you want to collect a great many samples it would probably be smarter and more economical to bring in an expert to survey the building and who can sample more strategically.

Interrupted Mold Growth Pattern on Building Drywall - Why Does Mold Growth Sometimes Stop in Straight Lines?

In our photographs shown above the thick black mold growth on drywall in a wet basement appears to nearly "stop" in a neat horizontal line just about four feet from the floor surface. Why?

Stachybotrys chartarum, which dominated the mold on this drywall, really likes wet conditions. As we explained above, the genera/species of mold growth may vary on a surface of the same material as a function of variation in moisture levels in the material.

In our photo at above right we show by having made a test cut into the moldy drywall that mold growth stopped its rapid advance up the drywall when it encountered the horizontal tape joint between the lower and upper runs of drywall in the building. We have found two common explanations for this observation:

1. The moisture wicking upwards in drywall from a wet floor is interrupted where the paper-covered edges of two horizontal runs of drywall abut.
2. Mold growth on joint compound alone is often significantly less in a building than on paper-covered drywall in the same area. This observation describes the success in "paperless drywall" sold for some applications.

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FIND MOLD in BUILDINGS, HOW TO
  CHOOSE SAMPLE POINT
  SAMPLING DRYWALL
  SAMPLING MISTAKES
  USE A FLASHLIGHT
HIDDEN MOLD, HOW TO FIND
  Photo Guide to Finding Hidden Mold
  Recognizing Cosmetic 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
  Wall test cuts to spot hidden mold
  Light colored toxic molds
  Moisture Gradients and Mold
  Other Places to Look for Hidden Mold
  ATTIC MOLD
  BATHROOM MOLD
  BASEMENT MOLD
  BLACK MOLD, HARMLESS COSMETIC
  CARPET MOLD CONTAMINATION
  CARPET TEST GUIDE
  CRAWLSPACE MOLD
  DRYWALL MOLD
  DIRT FLOOR MOLD CONTAMINATION
  ESSENTIAL STEPS IN FINDING MOLD
  FLASHLIGHT HELPS FIND MOLD
  WHAT MOLD LOOKS LIKE
  Black Mold  Brown Mold
  Green Mold  Red Mold
  Yellow Mold  White Mold
  Invisible Mold
  Recognize Cosmetic Mold
  Recognize Harmless Black Mold
    INSULATION MOLD
  SAMPLE POINT CHOICES FOR MOLD TEST
  SAMPLING MISTAKES
  USING LIGHT TO FIND MOLD

MOLD TEST KITS for DIY MOLD TESTS how to collect and send a tape sample to a laboratory

MOLD TESTING USING ADHESIVE TAPE
  What is Tape Sampling
  How Do we collect a Tape Sample

MOLD TESTING METHOD VALIDITY
  Tape sampling for mold
    Determination of mold genera
    Determination of mold species
    Shortcomings of tape sampling

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

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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

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