Mold testing is not really required
if the mold is highly visible, and there is no need to know
the type of mold that is growing. However, testing should
probably be done if it appears that pets or people have been
exposed to mold and the source is not apparent or the need to
know the specific type of mold is required for medical reasons.
Most mold testing is done by trained
professionals, but there are kits people can order for home testing. In
either case, the samples collected are normally sent to a laboratory
for analysis. In short, the individual gathering the samples
rarely analyzes the samples. Rather, in most cases, the
samples are transported under chain of custody protocols to a
licensed laboratory.
Sampling
There are two main types of samples. One
involves attempts to collect viable samples that can be incubated
and identified. This method provides more information and
can be important when the occupants of a property have had exposure
to a potentially dangerous mold.
Incubation increases the turnaround
time between collection and conclusions, but it is more accurate
from the perspective of identification. Non-viable samples are
easier to collect and can sometimes be almost immediately analyzed.
Viable Samples
There are two main methods for
collecting viable samples. One involves a moistened swab,
something like a Q-tip, that is gently rolled on a suspect surface
and inserted into a tube.
The other requires a piece of equipment,
usually an Anderson 6, that sucks air onto a petri dish containing
an agar. For those with a need to know, there is a sort
of pump, similar to what is used to force air into aquarium water. A
tube connects to a unit on a tripod that opens to permit the
placing of the petri dish. After exposure to the fine air
currents, the agar is pitted and looks a bit like the surface
of a golf ball.
Pros and Cons
If mold is visible, as with stachybotrys
growing on a wall, the swab is probably adequate.
The method based on air sampling
presupposes the spores are airborne. Some molds are more
mobile than other molds so a combination of methods yields more
complete information.
Another advantage of this method
is that samples of indoor and outdoor air can be compared and
relative counts are possible. These are measured in colony
forming units and give some idea of the relative importance of
the numbers.
Non-viable Samples
Testing for non-viable molds requires
almost no investment on the part of the person conducting the
tests.
Normally, tape is used and pressed
against a suspect surface. The samples are put into clean
plastic bags and sent to the laboratory. Transparent mailing
labels are often used for this purpose. The more sophisticated
labels are preprinted with a target area for the sample. They
also have control numbers. These labels are about the same
size as a microscope slide and make the work at the laboratory
very easy because of the target zone.
Another method, not as common,
is to suck air onto a prepared slide, sort of a variation of
the viable sampling method except that the stickiness on the
slide makes the sample non-viable.
Pros and Cons
Tape lifts are inexpensive and
quick, but they do not allow certain determinations to be made. Sometimes,
very similar species look more or less the same. Nevertheless,
these can be useful for clearance testing following remediation.
With tape lifts, no information
on density is possible. For instance, if a sample is taken
on two surfaces, six inches apart, and the two results are radically
different, one still does not have a clear sense of the magnitude
of problem.
The method using a prepared slide
has the same shortcomings in terms of identification, but since
the method involves testing of airborne spores, comparisons of
different rooms as well as indoor and outdoor air are possible.
Issues to Consider
Every test has two costs: the time
and labor of the person doing the tests and the laboratory charges. More
tests means more expense. It could also result in more
information.
The analysis of the laboratory
results may also require interpretation, and there could be a
separate charge for this. This report may be generated
by software or online surfing of the person writing the report. It
pays to ask how the report would be written because the laboratory
results are just a print out of findings that do not have user-friendly
language.
Contamination of Testing
In my opinion, a result that shows
the presence of a particular mold is positive evidence of a problem. The
absence of such a finding can be almost meaningless because the
sampling method may have been faulty or the handling of the samples
did not meet industry standards or the laboratory itself could
be inadequate.
As noted, with something like a
tape lift, there can be extraordinary differences in results
by just moving the tape a few inches one direction or the other. Negative
results therefore mean almost nothing whereas positive findings
are definitely indicative of something requiring further attention.
Failure to culture something only
means that the spores were not viable or the agar was not handled
properly or something happened between the time of collection
and incubation to inhibit the growth of the molds. According
to the National Association of Mold Professionals, laboratories
are only 30% accurate. This figure is used in comparison
with mold dogs, specially
trained dogs who sniff for mold, rather
the gases produced by molds. They have 97% accuracy rating.
The dogs are trained to point to
the infected area. That area is then inspected and samples
are taken. Someone wanting to determine how extensive mold
contamination is can consider employing a tester who has a mold
dog. A dog is capable of inspecting an office building
with 200 rooms in eight hours!
Ethical Concerns
Mold, if found, requires remediation. For
an individual concerned about mold, it is extremely important
that the person doing the testing can be trusted. If the
tester is also the remediator, he has a conflict of interest
because recommending more work than is necessary is unethical. Likewise,
if the tester is motivated not to find something, one can be
almost certain he can conduct the tests to produce this result.
Keep in mind that mold is microscopic. Moreover,
when magnified, a single slide possesses a simply enormous amount
of information, often taking a long time to survey. Targeting
a single square with a piece of lift tape reduces the size of
the sample to a manageable area, but eye strain and other factors
can affect the examination of the slide.
For an individual concerned about
health or property, it is important to have accurate tests. For
this reason, using a qualified, neutral person is the first step
towards getting honest results. Ask questions, get referrals,
find out how much training the tester has, which laboratory he
uses, and see if he really knows his subject.
