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Definition of Type 1 Errors & Type 2 Errors Effects of Type I or Type II Errors on
Mold or Environmental Testing
POST a QUESTION or COMMENT about how to report the density or level of mold or other particles found on indoor surfaces or in indoor dust samples
Definition & examples of Type 1 & Type 2 errors:
Classes of testing or statistical errors applied to mold or other environmental tests, inspections & reports can be divided into two basic mistakes or error types as we explain here. We include the definitions of type 1 and type 2 errors and we give examples of type 1 and 2 errors in building inspection and testing for mold contamination.
It is important to understand these types of environmental testing mistakes in order to reduce unnecessary risks to building occupants (failing to detect and report an environmental hazard) as well as to avoid wasting people's time and money focusing on on-problems (reporting as hazards conditions that are in fact not hazardous).
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Definition & Practical Examples of Type I and Type II Errors in Building Environmental Testing for Mold or Other Contaminants
Types of Reporting Errors in Buildings: definitions of Type 1 Errors & Type 2 Errors
Using building environmental testing for mold contamination as an example this article describes the types of errors that may be made by thinking, technical, or procedural errors during an investigation or test.
Type One Errors - missing a problem that's present: Occasional occurrences of certain mold genera in samples might suggest a hidden
or un-noticed mold problem in the building somewhere other than at the spot from which the sample was collected.
This is particularly true if the sample was collected by someone who is not expert at building science, indoor air quality, mycology, and related disciplines.
Examples of Type I errors during a mold investigation include:
Focusing on "toxic black mold" and missing a dangerous reservoir of hard-to-spot light colored mold contamination
Focusing on visible mold on building surfaces, defining a remediation plan based on visible mold, and failure to consider the possibility of significant problem mold reservoirs that are hidden in building insulation or building cavities
Errors in mold sample location selection: Where to stick adhesive tape for a surface sample, or where to place an air sampling device is of critical importance. If tests are performed in building areas remote from a large problem mold reservoir the tests may find little or no indication of a problem.
Errors or variations in the mold or other environmental test conditions: building conditions such as windows or doors open or shut, presence of people or animals in the building or not, fans on or off, heat or air conditioning on or off, and variations in indoor temperature and humidity all can make 1-4 orders of variation in the level of airborne particles in a building.
Type II Errors - asserting that a problem is present when it is not: Conversely, occasional occurrences of certain mold in samples might also seem to point a problem in a building where in fact none is present.
This is a greater risk where mold "counts" are used in
air sampling than it it is when surface sampling is combined with visual inspection. Occupant
indoor air or environment-related complaints or a building history of leaks
can suggest that additional investigation is in order.
Examples of Type II errors during a building mold investigation include:
Insisting that all "black mold" is "toxic black mold" when some is harmless.
Allowing fear of mold to launch a costly investigation or cleanup project for trivial mold growth such as a few square inches of mold growth on bath tile grout.
See MOLD / ENVIRONMENTAL EXPERT, HIRE ? for help in determining when the risk indicators justify the cost and trouble of hiring a mold or environmental expert
To avoid both Type I and Type II errors in measuring toxic or allergenic mold exposure
the building consultant needs to understand mycology (e.g. what mold is likely to grow in buildings), the significance of the particles found (e.g. Pen/Asp spore chains vs. individual spores), the history, construction, and materials in the
building and the details of the inspection itself when interpreting the importance of low levels of mold in building samples.
The articles recommended at the end of this page provide more examples of sources of Type 1 or Type 2 errors during building mold or environmental inspection, testing, lab sample analysis, & reporting.
Avoid This Building, Mechanical System Or Indoor Environment Troubleshooting Mistake
When making an observation, be sure that we are seeing what's really there, not what we want to see or what we failed to see, that is, seeing a pattern that isn't there or failing to see a pattern that is there.
In discussing studies of bird behavior, Joan E. Strassmann notes:
Snell-Rood and Cristol made sure to conduct this experiment blind, meaning that they did not know which birds had been held in captivity and which had not.
Not knowing which bird was in which group when taking down observations is important in just about any scientific study to avoid the danger of inadvertently seeing a pattern rather than seeing what is really there.
- Strassmann, Joan E., Slow Birding, the Art and Science of Enjoying the Birds in Your Own Backyard, TarcherPerigee (October 25, 2022) ISBN-10 : 0593329929 / ISBN-13 : 978-0593329924
...
Continue reading at MOLD TESTING & SAMPLING MISTAKES for more examples of how mold testing goes wrong, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
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In addition to any citations in the article above, a full list is available on request.
ENVIRONMENTAL HEALTH & INVESTIGATION BIBLIOGRAPHY - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc. Factors contributing to mold growth in buildings are discussed in-depth at
Mold
Standards: Levels on Surfaces in Buildings provides information about allergenic, infectious, and levels of toxic
mold in residential buildings - at what point does the amount of mold in a building prove likely to be a problem for the occupants?
Mold Exposure Standards: Exposure Standards for Mold, Levels of Severity of Indoor Mold Contamination - Various Published Standards of Permissible Mold Exposure Limits: at what level is toxic or allergenic mold a problem? - What does your "spores per cubic meter of air" or "spore count" really mean - if anything?
MOLD EXPOSURE RISK LEVELS: How to Determine Mold Contamination Probability or Mold Exposure Risk Levels in Buildings Based on Visual Inspection
Mold Level Reporting: How to Report Mold Levels in Mold Test Samples of Surfaces in Buildings
MOLD LEVEL IN AIR, VALIDITY: airborne density counts of mold spores per cubic meter of air - how to interpret low mold spore trap count results
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
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, [PDF] 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
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
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
Disease Prevention in Home Vegetable Gardens [PDF], Patricia Donald,Department of Plant Microbiology and Pathology,
Lewis Jett Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
"Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, - 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.
Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English)
US EPA: Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.