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Carpet test procedures using adhesive tape or vacuum cassettes:
This article describes & how to collect mold, allergen, or other particle or mold test samples
from carpets, furniture, drapes, or other soft surfaces to
aid in the diagnosis of the cause of interior wall, ceiling, flooring or carpeting stains and explains how to recognize their probable cause and source,
including soot stains, house dust stains, pet or animal stains, and thermal tracking or thermal bridging stains associated with
building air leaks, and building insulation defects.
How to Collect Indoor Mold, Allergens, Dust, Debris, or Stain Particles from Carpets or Other Soft Surfaces for Microscopic Lab Analysis
Often carpet and other indoor stains are mistaken for toxic indoor mold - they may not be mold at all. When investigating a building for a mold problem, you can save mold test costs by learning
how to recognize MOLD APPEARANCE - STUFF THAT IS NOT MOLD or is only Harmless Mold (Recognize Harmless Black Mold) but may be mistaken for more serious contamination
- save your money.
Because some clients have on occasion sent
samples to our mold test lab that really should not have been collected, much
less looked-at, we provide this library of photographs of things that are "not mold" and don't need to be tested.
These are substances that you can easily learn to recognize in buildings.
Save your mold test money, and increase the accuracy
of your mold contamination inspection or test for toxic or allergenic mold in buildings: review
these items to learn recognize non-fungal materials or even possibly harmless cosmetic
"black mold" often mistaken for "toxic fungal growth."
How to Collect Tape Samples of Stains, Dust, or Debris on Hard Surfaces or Surfaces with Visible Mold
For particles or stains found on hard surfaces indoors such as walls, ceilings, or furniture, or where mold growth is visible
on any surface including carpeting or furniture, often a simple adhesive tape sample
will perform well.
Furthermore, this sampling procedure is itself diagnostic, since if the adhesive tape is unable to lift and collect
any particles from the surface, that also tells us something about the type of staining present.
But remember that even an apparently
"clear" tape sample (when viewed by the naked eye) may contain important diagnostic particles which will be quite evident when
viewed as a properly prepared microscopic sample and at proper magnification and lighting in a forensic microscope.
Caution: Surface samples of mold growth on a soft material such as floor carpets or upholstered furniture may identify
what is growing on the surface but it may fail to identify what is growing inside the same material if a different
mold genera or species is present in that location.
Qualitative Analysis (what particle types dominate a sample) of Carpet Dust Samples
We use an air-sampling cassette connected to a vacuum pump to collect debris from carpets, upholstered furniture, or carpets.
In the hands of an experienced investigator a useful non-quantitative analysis can be performed to collect particles which, examined
in the lab, can tell us the dominant particles present in the debris.
The lab should also be asked to cite other particles, even occurring
at low levels, if the particle type is particularly diagnostic of a potential indoor air quality problem.
An example is the presence of
chains of Penicillium/Aspergillus mold spores since when found occurring in chains, these spores are suggestive of a nearby
(potentially toxic or allergenic) mold contamination problem.
What is the Consistency of the Vacuum Method for Testing Carpets, Couches, Curtains, or Other Surfaces for Mold or Other Particles?
As you can see in the photograph of sampling cassettes
above, we may use a template to define a four square inch area to be vacuumed. While it is a simple matter to define a consistent
area size when using vacuum methods to test soft surfaces such as carpets or couches, it is very very difficult to
actually sample these surfaces in a manner which is quantitatively consistent from sample to sample.
While some independent
studies have attempted to explore this question by "seeding" a carpet surface with a known quantity of particles, we are
very doubtful of the conclusions by some investigators if they assert that sampling consistency can be achieved.
consistency cannot be achieved, the quantitative comparison of samples from different areas is a tricky business,
and except for findings of the presence or absence of high levels or dominant-particle levels of certain particles in a
carpet vacuum sample, our view is that more detailed findings should be viewed with caution.
Here are some sources of inconsistency in vacuum sampling of soft surfaces:
Sample location Debris level: Variation in the amount of soil, debris, or particles in different locations on the surface to be sampled.
Two successive vacuum samples of the very same spot are likely to produce different results since each sampling removes some particles.
Two vacuum samples of nearby spots on a carpet may produce different results because of variations in the level of debris by area.
Sampling Location Traffic or Cleaning Level: Vacuum sampling of a high traffic area of a carpet or vacuuming an area of carpeting which is easily reached
during regular or special carpet cleaning processes may produce a very different result than a vacuum sample collected from
an area exposed to (or not exposed) to settling particles, mold growth, variations in moisture level, or ease of access for ordinary cleaning
Pile depth: Variations in pile depth of carpets or other fabric surfaces
Moisture Levels: Variations in moisture exposure of different areas of carpeting which is suspected of mold contamination
Particle collection efficiency: the percentage of particles captured by adhesive type sampling cassettes varies by particle size and
velocity; if the sampler is not designed for collection of the particles of interest, or as is very common with vacuum samples of surfaces
containing a high level of debris, if the adhesive surface becomes blocked by particles, subsequent material entering the sampler is lost,
making any quantitative analysis questionable.
Sample area size: Variations in sampling area size
Vacuum strength: Variation in the vacuum strength of the sampling pump itself. Especially if a battery-operated pump is used, the pump strength may vary during use as battery level declines.
High Efficiency Vacuum Sampling Methods for Carpets or Other Surfaces
Other vacuum methods which use a calibrated flow rate and a sampling filter can collect nearly 100%
of the particles from a surface, permitting a quantitative analysis of the number of particles per square inch. In our OPINION this is often a rather
Even studies which claim to report that the results of this sampling method are repeatable (a measure of sampling
method reliability) we find that there is an enormous variation, probably several orders of magnitude, in the number and possibly even the type
of particles collected in such samples depending on the investigator's choice of sampling location, sample duration, vacuum strength, and other factors.
The result may be an analysis which is impressive in its precision, say giving 1,243.275 particles of particle type X per square inch of
surface, but completely inaccurate (because there maybe so much variability due to sampling procedure that sampling an area one foot away
gives a particle level of 124,327.5 particles per square inch.).
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