How to Report Mold Levels in Mold Test Samples of Surfaces in Buildings
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• How to report mold levels in buildings
• Mold test & reporting procedures

The purpose of this brief paper discussing how to report levels of mold in buildings is to seek consistent use of surface particle mold test adhesive tape sample descriptive language among microbiology lab and field investigation professionals. I define levels of significance of mold findings in test results. The definitions that follow are a work in progress and need support by example lab photomicrographs and quantitative study. © Copyright 2008 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.

If collected by an expert during a careful visual inspection, and thus if representative of conditions in a building, surface particle samples collected in buildings provide an important building diagnostic which can be expected to be more reliable than other popular mold testing methods including some which, sadly, may be little more than junk science. If an indoor particle sample is representative of the area being inspected, then the identity of significant or dominant particles present is important information about conditions in the building.

When we examine surface test samples collected in buildings, properly obtained by following a visual inspection of the building and by using a clear, consistent sampling procedure, then we can report the following Non-Quantitative Particle or Mold Levels Based on Samples

My mold level terms "Significant/Dominant, Present, Incidental" are defined below. Others may use similar terms such as "heavy, medium, light", or "high, moderate, low. "

1. Particles not detected in a sample means that the particle named was below the detection limit of the inspection, sampling, and examination methods used in the field and laboratory. It does not mean that none of these particles are present in the building.
2. Particles Incidental in a sample means that I found only occasional, or low-levels of fungal spores in the sample provided-below the level I usually find in indoor air samples in buildings where there has been a history of leaks, flooding, or known mold contamination. This is a positive description of the quality of indoor air insofar as fungal spores are concerned, but one cannot unequivocally conclude that there is no possible health hazard present because: 1. individual exposure, sensitivity, and health status vary widely; 2. even a zero count does not guarantee that a particle is not present in the building. It means only that that particle was not in the sample provided. A careful, expert look at the building may disclose particles that an occupant or inspector was unable to recognize and thus did not send to the laboratory for determination.

Type I 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.

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 surface sampling combined with visual inspection. Occupant indoor air or environment-related complaints or a building history of leaks would suggest that additional investigation is in order.

To avoid both Type I and Type II errors 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.

3. Particles Present in a sample means that these particles were frequently present in the sample. They are less likely to be of significance to occupants of the building than "Significant/Dominant" particles except when particles named 1. are particularly allergenic or toxic 2. suggest an undiscovered building problem. If the building has a history of leaks, water entry, or other hidden moisture problems, the presence of even a few toxic or allergenic spores which are not often found in outdoor air samples may indicate a hidden problem. If control samples from outdoors or from non-complaint areas of a building do not show the presence of these particles, further investigation is in order to determine if there is a significant presence elsewhere in the building than from where this sample was taken.
4. Particles Significant/dominant in a sample means that within the sample these particles were the most-frequent particle in the sample or that the particle was present in most or all sample focal fields under the microscope at 400x or higher magnification. Problematic mold or allergenic particles listed in this category are likely to be of significance to occupants in the building. Where the particle is a mold genera or species capable of growing indoors a finding at this level makes it likely that there is one (or more) mold reservoir or mold colony in the building. This term refers to the sample content itself. A visual inspection of the property is needed to determine if the mold is present in extensive or large areas in the building. When the significant/dominant particle(s) present is/are allergenic or toxic mold or an allergen, building investigation to find and clean/remove the problem source is needed

More Information on Testing and Reporting Mold Problems in Buildings & Building Diagnostic Inspections and Repairs

Factors contributing to mold growth in buildings are discussed in-depth at
Mold 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 Testing: Bulk Samples and Their Interpretation - a quick tutorial  
Mold Testing: Air Samples and their interpretation - a quick tutorial describes air sampling, its uses & shortcomings
Mold Testing: Validity of Cultures (settlement plates or swabs) to find toxic mold in buildings describes the shortcomings of these approaches which are invalid when used alone.
Mold Spore Counts in Buildings: are indoor fungal spore counts valid?
Mold Classes in Buildings: cosmetic, allergenic, or toxic mold in buildings
Mold Investigation Reports and Mold Test Lab Reports: What to Look For outlines a professional, useful mold investigation report.
Mold Risk Levels in Buildings Based on Visual Inspection
and our Mold Information Center: What to Do About Mold in Buildings provides a list of key resources about indoor environmental concerns with mold.

InspectAPedia ^® Home & Site Map - Building Inspection, Diagnosis, & Repair, Environmental Inspection & Testing - Research Website

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

Home Inspection Construction Consulting Services & advice for home buyers

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Contact Daniel Friedman for website content suggestions or for fee-paid consulting

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