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How to Report Mold Levels on Building Surfaces Using Tape Samples of Indoor Surfaces and Indoor Mold InspectAPedia®  -     How to report level of mold contamination on building surfaces Using and reporting on tape samples to check for mold on building surfaces

Here we discuss how to report and understand the significance of the level of particles of mold or other particles found on indoor surfaces. Readers should also see MOLD TESTING USING ADHESIVE TAPE where we provide a quick tutorial on "Mold Testing: Bulk or Tape Surface Samples and their interpretation"

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.

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Reporting the Level of Mold Contamination on Building Surfaces

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

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

Depending on where a tape sample is collected, moving the sample source by as little as on inch can completely change both the quantity of mold present (by several orders of magnitude) and actual genera/species detected. Therefore quantitative reporting of mold concentrations found on surfaces (such as spores/M³ or CFU/M² on a surface) in buildings should not be attempted except for narrow purposes of scientific research under controlled conditions. The variation in tape and other sampling methods is explored at MOLD TESTING METHOD VALIDITY.

The purpose of this paper is to seek consistent use of surface particle sample descriptive language among microbiology lab and field investigation professionals. The definitions that follow are a work in progress and need support by example lab photomicrographs and quantitative study.

1. 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
2. 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.
3. Particles Incidental in a sample means that we found only occasional, or low-levels of fungal spores in the sample provided-below the level we 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 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.
4. 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.

Types of Mold Level Reporting Errors in Buildings

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 we 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.

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ENVIRONMENTAL HAZARDS GUIDE
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also see ACCEPTABLE MOLD LEVEL
MOLD EXPOSURE RISK LEVELS
  L1: Very-Low Mold Risk
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MOLD LEVELS on SURFACES
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MOLD PREVENTION GUIDE
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