Molds

Methods in Monitoring Mold in the Environment

Based on this article, household molds can often be inspected by using a inspection microscope and can be detected by sight or smell. A musty odor generally accompanies mold growth as well as a whitish, greenish, brownish, blackish or orange discoloration 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.

Based on this article, it explains that there are 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 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 equipment. Samples are washed to transfer the mold into a solution in a lab. A portion of this solution is then stained so that when illuminated with fluorescent light, the mold can be more easily seen under an inspection microscope. By viewing the mold in an inspection microscope, the types of mold that were on the building materials can be determined.

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 inspection 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 an inspection 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 is 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.

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 an inspection 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 an inspection microscope, but this method has the disadvantage of not being able to quantify the viable spores. Read the entire article