Mold Testing Methods Surface Samples

By Daryl Watters

When a mold inspector takes bulk, tape, carpet/dust, or swab samples, spore numbers are not compared quantitatively to outdoor levels. Thus, the number of spores in these types of samples often are not as meaningful as the numbers found in air samples. Also, because the air is not being tested, your inspector cannot say for sure how much if any of the mold sampled from surfaces is in the air you are breathing. However, these samples can be helpful because they typically provide the analyst with more than just the mold spores so that identification of mold type can be more accurately conducted by viewing various structures of the mold, not just spores. In addition to providing more structure for direct microscopic examination, bulk samples are sometimes grown in the lab or run through PCR testing for analysis to the species level.

Mold Testing with Tape

When a tape sample of actual mold from a moldy surface is taken using Biotope, a clear piece of Scotch Tape, or a sticky Cyclex slide, the sample will often show entire mold structures including spore forming structures and hyphea. These can be used to confirm mold growth more confidently and rule out the possibility that the sample was just settled spores only.

Mold Testing of Bulk Samples

When a bulk sample of actual mold or moldy material is sent to a lab, the lab may use clear Scotch Tape to take a sample from the bulk mold material for examination under the microscope. The lab may culture some of the bulk mold specimen in a petri dish for analysis of the colonies to the species level.

Mold Testing of Carpet Dust

When a dust sample is analyzed it may be place on a slide for direct examination to view spores hidden in the dust directly. This is a very common method used by most mold inspectors labs and has become accepted in the industry. This popular method may be helpful but many spores are not seen because spores are hidden behind dust, or the spores blend in well with dust. The lab will often report very low spore levels even if the carpet sampled was obviously very moldy. This inspector has seen this happen many times with various dust samples tested at different labs. When studies are done on what are normal and what are elevated spore levels in carpet dust, the scientist working on the projects and the mold labs they utilize for dust analysis use very different methods for analysis.

They wash the dust and dust filter out of the collector with a mild solvent and culture the spores in a petri dish. This method will typically reveal tens of thousands of spores or even hundreds of thousands or millions of spores. Your inspector must be aware of the different methods and the different results to be expected when interpreting dust sample results.

Mold Testing with Swabs

A sterile swab provided by a microbiology lab is sometimes used for sampling. This inspector dislikes this method because unlike when using tape, the mold structures are always broken up when using swabs. Therefore, meaningful mold structure identification and spore counting cannot be done when testing mold with swabs. Many poorly trained mold inspectors will use a swab on nearly every inspection done, not because of a well thought out sampling plan, but simply because the lab gave them swabs.

About the Author: Daryl Watters has a bachelors degree in education for teaching biology and general science and is a certified mold inspector, certified home inspector, and certified indoor environmentalist providing building inspections in South Florida since 1993. For more information visit floridamoldinspectors.usflorida-mold-inspection.com

Source: isnare.com

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