SURFACE SAMPLING OVERVIEW

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SURFACE SAMPLING OVERVIEW
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There are other simple sampling methods that may
be used to supplement volumetric air sampling.
Surface samples are taken by tape lift imprint,
by swabbing the suspect surface with a culturette
swab, or by submitting a bulk sample of the
suspect surface. We typically recommend that a
direct microscopic examination be performed on
surface samples.
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While culturing a surface sample may help resolve
a specific identification problem, used alone
such a culture may result in an inaccurate
characterization of the surface sampled. A direct
microscopic examination of a surface shows
exactly what is there, without being affected by
an organisms ability to compete and grow on
sampling media.
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The primary purpose of a direct microscopic
examination of a surface is to determine whether
or not mold is growing on the surface sampled,
and if so, what kinds of molds are present.
Secondarily, most surfaces collect a mix of
spores which are normally present in the
environment. At times it is possible to note a
skewing of the normal distribution of spore
types, and also to note marker genera which may
indicate indoor mold growth.
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In addition, when mold growth is present indoors,
many more spores of a particular type will be
found trapped on surfaces. These spores may be in
forms which indicate recent spore release (close
proximity), such as spores in chains or clumps.
Marker genera are those spore types which are
present normally in very small numbers, but which
multiply indoors when conditions are favorable
for growth.
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These would include cellulose digestors such
asChaetomium, Stachybotrys, and Torula. While a
singleStachybotrys spore is occasionally seen as
part of the normal outdoor flora, finding 5 or 6
of these spores on a single scotch tape slide of
a duct surface is an indicator thatStachybotrys ma
y be growing indoors.
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Pros A direct microscopic examination of a
surface shows exactly what is there, without any
skewing by laboratory procedures. Surface
sampling is inexpensive and (for a direct
examination) may be analyzed immediately. Surface
sampling may also reveal indoor reservoirs of
spores which have not yet become airborne.
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Cons The presence of biological materials on a
particular surface is not a direct indication of
what may be in the air. Health problems related
to indoor microbial growth are generally caused
by the inhalation of substantial numbers of
airborne spores, sometimes over a substantial
period of time (exceptions being, for example,
situations involving small children or
immuno-compromised individuals).
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