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Here we discuss the use of mold test swabs to collect mold test samples to screen buildings for harmful indoor mold, followed by a discussion of PCR for mold identification and building mold screens. In this article series discuss the validity of nearly all of the popular mold testing methods currently in use, pointing out the strengths and weakness of each approach to mold sampling in the indoor environment, beginning with air sampling for airborne mold levels indoors. The appropriateness of testing at all is discussed on this and other pages at our website. Because mold test validity and mold test accuracy are often confused, readers should also see ACCURACY OF VARIOUS MOLD TEST METHODS. People who need to conduct mold inspection and testing indoors should see MOLD TEST PROCEDURES and TECHNICAL & LAB PROCEDURES.

Our MOLD INFORMATION CENTER includes more broad discussions of the overall approach to building investigation, as do many expert references cited at that web. For a more comprehensive collection information about mold test methods see INDOOR AIR QUALITY METHODS COMPARED. For more on "mold classes" (Cosmetic mold vs. allergenic mold vs. toxic or pathogenic mold) see MOLD CLASSES, HAZARD LEVELS and more references such as a Mold Action Guide are at the end of this document.

© 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.

A Guide to Swab Sampling to Screen for Toxic Mold:

Swab samples can be used to pull particles for microscopic exam but destroy the identifying conidiophores and hyphae; They are more often used to prepare cultures which have the shortcoming cited above. We make use of swabs to sample for bacteriological contamination.

A sterile swab is wiped across a sampled surface, the inserted into a sterile tube for mailing to a lab.
Swabs are processed in one of two ways:

1. Direct examination: The lab can lift particles from the swab using tape or other methods to make a direct particle examination similar to tape sampling above.
2. Culturing: The lab rolls the swab across a culture plate to culture the sample for identification.

Shortcomings of swab sampling for mold:

1. Direct microscopic examination of mold swab samples: determination of species by direct examination is often difficult as the collection method destroys or fails to collect identifying structures such as conidiophores and hyphae. "Rubbing" and possibly even "rolling" the swab on a surface to collect a sample will often destroy key structural components (the conidiophores and hyphal details) which would have been more easily preserved using adhesive tape.
2. Culturing from mold swab samples (or from mold tape samples): risks misidentification of the dominant species present and may completely miss species which are present due to choice of culture media and growing conditions. See Shortcomings of culturing for details.
3. Mold test swabs used to collect particles from insulation, fabric, upholstery, carpets, may fail to collect representative material as they only touch surface particles. Vacuuming such surfaces is more representative of what particles are aerosolized by human activity in a building.

Swabs are very effective for use in testing for bacteriological contamination testing but in our opinion they are of less use in fungal work.

A Guide to PCR Methods for Mold Identification

© 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.

Polymerase chain reaction (PCR) can be used to identify individual genera/species with good accuracy and fairly quickly. The method requires costly equipment and is not available at most laboratories. Perhaps more important is that the data base of PCR identification information is limited to a small set of species compared with the wide range of genera/species which occur.

At least one excellent national laboratory offers this service for mold speciation. Depending on how rapidly technology drives down the cost and how rapidly the identification data base is expanded, we suspect that this method will see increased use.

The limitations of PCR as a mold identification tool are currently two: first, it is quite costly to perform per sample, and second, it is excellent at identifying the presence or absence of a specific mold you're looking for. It is less useful as a broad spectrum scan expected to pop up with a result of what's present out of the 1.5 million possible candidates - of which only a few are yet even in the PCR database.

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MOLD TESTING METHOD VALIDITY
Introduction
  Air samples
    Shortcomings of air sampling
    Mold in Air: Quantitative Analysis
  Tape sampling for mold
    Determination of mold genera
    Determination of mold species
    Shortcomings of tape sampling
  Vacuum samples
    Surface vacuuming
    Shortcomings of surface and carpet vacuuming
    Vacuuming building cavities
    Vacuuming exposed insulation
    Shortcomings of vacuuming insulation
  Cultures to "Test for Mold"
    Shortcomings of culturing
  Swab sampling
  Shortcomings of swab sampling
  PCR methods for Mold Identification
  Mold "Testing" vs. Mold "Problem Identification"
  Are Mold Test Kits Useful?
  Reasons to Test for or Identify Mold
    1. Save Money if it's Just Cosmetic Mold
    2. Mold Related Illness
    3. Mold Cleanup Data baseline

• 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
• Craig Balchunas is an ASHI member, and a licensed New York home inspector and environmental and mold test inspector in Newburgh, NY.

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