InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
How much variation do we see when using Air Sampling to test for Mold Exposure or Contamination Levels in Buildings?
Here we demonstrate that indoor airborne mold or other particle counts vary enormously from minute to minute, providing highly inaccurate (though precise) numbers of spores per cubic meter of air. Here we answer these key questions about mold testing:
How much variation occurs when using air sampling to test for mold?
What is the range of variation in air test samples for mold and what does that say about the accuracy of air tests used to state mold exposure?
This is a brief tutorial which provides information about the accuracy of tests for the level of allergenic and toxic mold in residential buildings: Are
spore counts valid? Are cultures and swab tests valid? These critical questions are discussed in this series of articles.
There is normally very high variation in the level of airborne particles in indoor air from moment to moment in buildings.
Actual field data easily demonstrates that particle presence in indoor air varies by orders of magnitude from minute to minute.
quantities of air indoors just a few minutes apart regularly shows up in our data as enormous differences in particle density from interval to interval, as you
can see in this photograph of parallel traces of airborne particles captured by an air sampler which collected these samples just
minutes apart in the same location in a building.
We always see this phenomenon in buildings, since unless we are measuring airborne particles released
at a fixed rate in a controlled test chamber there are quite a few site conditions that agitate airborne debris.
A simple visual examination of the five traces of airborne particles captured on this microscope slide make clear that the variation in particle level is significant.
Further examples of wide variation of airborne spore counts indoors are provided at Particle Levels vs Sampler Height where you can see microphotographs of traces such as the ones above.
Don't Confuse Precision and Accuracy in Airborne Mold Spore Counts?
Some people are confused about the difference between precision and accuracy.
An airborne mold spore count obtained from a spore trap or similar air sampling device can be processed in an aerobiology lab or mold test lab by several methods of varying accuracy depending on not only the site variables (which dominate the airborne particle count, but also depending on the skill and experience of the lab technician, the quality of the microscope and slide preparation, and the percentage of the particle trace that is examined.
In the hands of a skilled microscopist who uses the best practices and who examines 100% of the particle trace, the resulting lab report can give mold spore count that is very precise - for example, citing 5,731 Aspergillus niger spores per M3 (cubic meter) of air.
But what the mold test field investigator and laboratory technician may not be able to report is that the variability from minute to minute in the airborne particle level was enormous, easily by a factor of 100.
If the mold test field investigator had collected her or his sample in the very next five minute interval using exactly the same equipment and methods and processing the sample in exactly the same lab with the same technician may produce a very precise count of 573,124 airborne mold spore count of Aspergillus niger spores per M3 of air.
The two counts are very precise (5,731 and 573,124), but the airborne mold spore count produced by this spore trap method is completely inaccurate: 573,124 mold spores per cubic meter of air is 100 times more mold spores per cubic meter of air than 5,731.
If your airborne mold spore count can easily vary by a factor of 100 from minute to minute it may be precise, but it is inaccurate, and therefore in many cases, especially in cases of low counts that appear to be below the threshold of concern in many mold standards, such counts are completely unreliable.
Just try waving a note book across a table before counting mold spores in air and check the difference in airborne spore levels.
Then review mold inspection and mold test reports to notice whether or not the field investigator has noticed and recorded building conditions that affect air current activity in a building: fans on or off, space occupied or unoccupied, heat on or off, air conditioning on or off, etc. Any one of these completely changes the airborne particle level indoors.
The realization that airborne mold spore counts or counts of any indoor airborne particle are inaccurate is a reason to perform a thoughtful visual inspection of and history taking of a building that is under investigation for air quality problems. But such investigations, properly performed, may be costly and often are unnecessary and should not be performed at all.
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Thanks to Susan Flappan, Flappan Consulting, moldetect.com, Overland Park KS, 913-402-1131, for contributing comments and some suggested text from ACGIH Bioaerosols: Assessment and Remediation 12/2006.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon) - The Atlas of Clinical Fungi is also available on CD ROM
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention in Home Vegetable Gardens,"
Department of Plant Microbiology and Pathology,
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold
Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold
cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings,
and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating
the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing
rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some
help from a licensed pest control expert.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones