Alternaria mold spores and hyphae from an indoor surface (C) Daniel FriedmanBuilding Insulation Mold Test

  • VACUUM TEST INSULATION CONTAMINANTS - CONTENTS: How to test building insulation for mold contamination - Guide to use of vacuum cassettes for mold screening. Find mold hidden in building insulation that looks clean. Photographs of mold contaminated fiberglass insulation
  • POST a QUESTION or READ FAQs about vacuuming building insulation to screen for mold or other hazardous particle contamination.

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Vacuum tests on building insulation to screen for mold or other particles:

Using Vacuum Cassettes or Spore Traps to Collect Mold or Particle Dust Samples from Building Insulation, this article explains the advantages and shortcomings of using vacuum cassettes or spore traps to collect mold test samples (or other dust or particle samples) from building insulation where mold, insect, or other contamination is suspected.

Our photo (page top) shows what looked like clean fiberglass insulation located over a basement that had been subject to chronic flooding and ultimately, mold contamination that was visible on other basement surfaces. Vacuum tests confirmed that the insulation contained high levels of Penicillium/Aspergillus mold spores and was acting as a mold reservoir in the building.

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Usefulness of Vacuuming exposed Building Insulation for Mold Contamination

Photograph of crawl space insulation which testing found to be mold contaminated.15th Annual North Carolina/South Carolina
Environmental Information Association Technical Conference
Myrtle Beach, SC
Daniel Friedman 23 September 2005, Updated 4/14/2009

At many investigations we have found a large hidden mold reservoir in building insulation, particularly fiberglass insulation in attics under roof leaks over drywall, and in crawl spaces which have been damp or wet. We have also found very moldy fiberglass in basement ceilings after moldy surfaces and debris have been removed (such insulation should have been removed during the remediation).

[Click to enlarge any image]

Our photo (left) shows insulation that did not display visible mold but that our vacuum test found to be very mold-contaminated (see our lab photo below). (The dark stains on this fiberglass insulation were not mold but house dust deposited from air movement.

Our method is to agitate the target insulation (simply poke it with your flashlight or a ruler), followed by holding our vacuum cassette an inch or two away from the insulation surface. This reliably picks up particles from the insulation without overloading the sample with fiberglass. (A baseline comparison sample collected in nearby building air before any such agitating sampling is also needed.) This method has been remarkably successful in finding and allowing the removal of several "mystery" problems in buildings where severe mold-related complaints were heard.

Photograph of mold spores of Aspergillus sp. found in crawl space fiberglass insulation.Any of several types of vacuum cassettes are used to collect dust from a surface. We use Air-o-Cel ™ cassettes and MCE filter cassettes. We am experimenting with vacuum cassettes loaded with high-adhesive tape.

The contents of the mold test vacuum cassette may be examined by light microscope or may be used for preparation of cultures. One special (and costly) cassette method collects dual samples permitting both direct examination and culturing.

Our lab photo (left) shows insulation that did not display visible mold to the naked eye when examined in place in the building (photo above) but that our vacuum test found to be very mold-contaminated.

This method may be used for both qualitative and quantitative analysis, depending on collection method details. It is best suited for sampling dust from surfaces and from soft goods such as carpeting or upholstered furniture.

It's strength is its use in examining multiple hard surfaces with relatively low levels of debris (avoiding sample overload) or individual soft surfaces where tape may not collect particles imbedded in the surface, and in collecting dust from multiple locations in a single cassette as a building dust scan for mold.

Shortcomings of vacuuming insulation for mold

We love this method, but one must take care not to overload the sample.

If insulation is not exposed for testing one needs to make a sufficiently large opening to agitate and then vacuum the insulation - we use a 4" square opening and take care to avoid vacuuming up simply a collection of drywall dust.

See FIBERGLASS INSULATION MOLD for a detailed discussion of hidden mold contamination in building insulation.


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.

Our MOLD INFORMATION CENTER includes more broad discussions of the overall approach to building investigation, as do many expert references cited at that web.


Continue reading at VACUUM CASSETTE FILTER SAMPLE TESTS for DUST / MOLD or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

For a more comprehensive collection information about mold test methods see INDOOR AIR QUALITY METHODS COMPARED.


Or see VACUUMING BUILDING CAVITIES - an approach that we have not found reliable, and an explanation of why this is so.

Or For more on other tests for mold and their strengths and weaknesses see

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