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Viable And Non-Viable Mold Sampling

Non-viable air samples refer to samples that are taken on some sticky media or on a filter membrane or tape and subsequently examined directly under a microscope for enumeration and identification of mold spores and hyphal fragments without culturing. In other words, the samples are taken for analyses by direct microscopic examination. This would be the best to take if the objective of air sampling was to have an idea of how contaminated the air is, then the data required would be total counts. Viable air samples refer to samples that are taken on some growth media and subsequently incubated for mold propagules (spores and/or hyphal fragments) to germinate and form colonies. The resulting colonies are then enumerated and/or transferred to other media for identification to genus or species. If the objective of air sampling was to find whether the air contains a specific species of mold e.g., Aspergillus fumigatus, then identification to species would be required. Since non-viable analysis would not distinguish A. fumigatus from other Aspergillus species and not even from Penicillium species and related genera, then sampling for viable analysis would be selected. Both method can be used in a mold investigation, it all depends on the objectives of air sampling, the data required and the questions these data are intended to answer.

Surface Sampling

Surface / Bulk sampling is used to identify a mold type at a specific location. This mold testing technique is useful also in ruling out possible discolorations or staining that sometimes exhibit mold like characteristics.

A cotton swab is used to collect a small quantity of material from a non-porous surface. The area where mold is suspected is gently swabbed. After the entire area has been sampled, the swab is inserted into the tube of a buffer and shipped to the laboratory within 24 hours of the mold testing. In turn the sample is analyzed either with a fungi screen or culture analysis. An accredited laboratory performs the testing procedures for these results.

A bulk sample should be collected when material is porous and swabbing is not practical. A utility knife is used to collect samples. Bulk materials are then placed into a standard zip-lock type bag and sent to an accredited laboratory to be analyzed with either a fungi screen or culture analysis.

A piece of clear tape is used to collect a small quantity of material. In turn this is analyzed either with a fungi screen or culture analysis. An accredited laboratory performs the testing procedures for these results.

Air Sampling
In mold testing, air sampling is the most effective method for determining whether a mold infestation is potentially creating an unsafe living environment. During this type of mold testing, air quality is tested using the Air-O-Cell cassette by drawing air and impacting the airborne particles over a glass substrate. Typically the processruns for 4 to 10 minutes.


 Samples of the indoor air and the outside air are taken for comparison. There should not be any mold inside the house that is not found outside. The concentration of mold inside a home should not be higher than the concentration of mold outside. Keep in mind that mold spores in the air being sampled can vary greatly in relation to the life cycle of the mold, atmospheric and environmental conditions, and the amount of ventilation. There are seasonal and diurnal variability in airborne mold at an indoor residential environment. Air sampling may be necessary if the mold growth is suspected (for example, musty odors), but cannot be identified by a visual examination. The purpose of such air sampling is to determine the location and/or extent of mold contamination as well as a simple confirmation that mold growth exists somewhere in the building. All mold spores have a source, and identifying the source is the goal.

The reason is, in some situations, you may have mold growing on surface, yet it has not reached a point where it is releasing very many mold spores into the air. In which case, air sampling alone would provide results that did not accurately portray the extent of mold growth. Or, you may have a situation where, in your random surface sampling, you did not sample a surface where mold was growing (or at least not at a significant level), but mold colonies throughout other parts of the home had reached a point where they were releasing substantial amounts of mold spores into the air. In this case, your surface sampling would not give you and accurate picture of the problem.

Mold tests can be divided into two categories: air and surface. If you find it necessary to perform a mold test, then it would be advisable to take at least one surface sample and one air sample.