American Mold Investigations, toxic mold, orange county mold inspections, los angeles mold inspections, southern california mold inspections

Mold Inspections:
Methods for Monitoring Mold in the Environment

Household molds can often be detected by sight or smell. A musty odor
generally accompanies mold growth as well as a discoloration (white,
green, brown, black, or orange) of the surface that the mold is growing
on. If there is visual confirmation of mold growth, further testing is not
usually necessary; instead, immediate steps should be taken to control
the problem.

There are, however, some instances where a sensory assessment is
not sufficient: a person contracts a disease that could be a result of
exposure to a certain species, so identification of fungal types is
necessary; symptoms of mold exposure are exhibited by individuals,
but a visual inspection does not detect mold; a ventilation system is
suspected of being contaminated and the extent of mold growth needs
to be quantified; or comparisons of outdoor and indoor air quality are
needed, so the types and quantities of mold present must be obtained.

Just as there are many types of mold that can contaminate indoor air
quality, there are many methods that can be used to detect molds.
There is not a single method that can effectively detect the types and
amounts of each mold in a building, so often times a combination of
detection methods are used to sample indoor air quality.

Sampling Methods

Commonly used methods used to detect the presence of mold in a
building include bulk sampling, surface sampling (swab or tape), and
air monitoring for bioaerosols.

•        Bulk Sampling

Bulk sampling involves collection of material samples in a building from
areas where mold is apparent or if no mold can be found, where
conditions exist for the growth of mold such as water-damaged floors
or walls. To prevent mold from one sample getting onto another
sample, samples are collected and bagged using sterile equipment4. In
the lab, samples are washed to transfer the mold into a solution. A
portion of this solution is then stained so that when illuminated with
fluorescent light, the mold can be more easily seen under a
microscope. By viewing the mold in a microscope, the types of mold
that were on the building materials can be determined. Another portion
of the solution is put into a dish that contains the nutrients molds need
to grow. After being incubated, the organisms in the solution that are
alive will form visible colonies in the dish that can be identified and
counted. The disadvantage to the bulk sampling method is that parts of
building materials need to be removed or damaged in order to obtain a
sample.

•        Surface Sampling

Surface sampling allows the identification of molds that are growing on
a surface in addition to molds that settle out of the air onto surfaces.
The two techniques used for sampling surfaces are swab sampling and
tape sampling. Swab sampling involves using a sterile swab to wipe a
known area of a surface to collect the mold, and tape sampling involves
using a clear piece of adhesive tape to strip a surface suspected of
having mold on it.

The analysis of the swab method is similar to that used in the bulk
sampling method. The mold is transferred into solution and then
subsequently one portion is viewed under the microscope and another
is grown in a dish with nutrients. This analysis is performed to identify
both the types of mold present and the number of viable or live
organisms that were in the solution. The adhesive tape is viewed
directly under a microscope to identify the types of mold present on the
sampled surface.

There are disadvantages involved with surface sampling. The smoother
the surface sampled, the more effectively the tape or swab can pick up
the mold. It is hard to sample surfaces using these methods if they are
rough, uneven, or porous. Using swabs to sample limits the
identification of mold types because some of the organisms are
destroyed during the sampling whereas using tape to sample keeps the
structure of the organisms in tact for identification. The downside of
using the tape, however, is that the mold cannot be removed from the
tape after it is sampled. This means that samples taken using the tape
method cannot be cultured to see what portion of the mold organisms
are living. Tape sampling also requires that the surface being tested not
have a lot of other debris on it. A tape sample that contains a large
amount of debris makes it hard to identify the mold.

There are also advantages to using surface sampling methods.
Because multiple samples can be taken from stationary surfaces,
surface sampling can determine either the presence or absence of
mold in certain areas, and be used to compare the amount of
contamination in one area to another. Furthermore, unlike bulk
sampling, both swab sampling and tape sampling are nondestructive
methods which do not include the removal or damage of any materials
in the building. Surface sampling requires little in the way of costly
materials or equipment, it’s relatively easy to perform, and the results of
the sampling can be obtained quickly.

•        Air Monitoring

As with all areas to be sampled, there are a number of ways to monitor
the air for bioaerosols. A passive method used to determine the types
of mold in a given area involves only exposing a dish filled with
nutrients, called a settling dish. This process requires little effort on the
part of the operator, but it does not give a representative view of the
number or type of organisms in the air only the ones with enough mass
to settle out of the air onto the plate.

Active methods collect samples using a pump that draws air across a
nutrient dish, through a filter, or over a greased slide. If a dish of
nutrients is used it can be incubated directly to identify the types and
quantities of mold in the air. Using a filter or a slide to collect a sample
versus a nutrient dish has the advantage of allowing the total amount of
mold in air to be accounted for and not just the viable or living portion.
After mold is collected on a filter, it is suspended into solution were it
either can be viewed under a microscope or incubated in a nutrient
dish. A sample collected on a greased slide sometimes referred to as a
spore trap can be viewed directly under a microscope, but this method
has the disadvantage of not being able to quantify the viable spores.

As with other methods, the results of the air sampling methods alone
cannot eliminate the possibility that contamination exists. One reason
why data from air sampling methods cannot conclusively prove the
absence of mold is that different varieties of mold favor different
methods of sampling and analysis. Another reason that an air sample
may not represent the molds that are present in a building is that
sampling may have been performed during a time when the mold was
inactive.