Mold


 

Mold has become a controversial subject over the last five to ten years, due to the fact that more and more industries (such as real estate companies, builders, etc.) have been forced to deal with the issue. Most of these companies follow the guidelines in place to properly deal with mold, yet others try to trivialize the effects of mold because it makes their jobs more difficult. For example, it is hard for a real estate agent to sell a house affected by mold growth. Therefore, some of these individuals take the position that ‘mold is harmless, bleach it down and you’ll be fine.’

 

The truth is that exposure to high concentrations of mold spores in the air will illicit some symptoms in most individuals. Obviously, people who are sensitive to mold allergens will experience symptoms more quickly and severely. Individuals with compromised immune systems (elderly, young children, HIV, organ transplant, etc.) must be very cautious because they may be susceptible to mold infections.


Another thing to consider is that many insurance companies include some degree of mold coverage (often limited to $10,000). These companies would not spend literally millions of dollars a year on mold testing and mold remediation unless there was a solid scientific backing saying that those costs were justified.

When dealing with a potential mold problem, you want to consider the following:


•       Cause of mold growth

•       Amount of mold growth (visible & hidden)

•       Type of mold growth

•       General health of building occupants

 


 

Mold Testing

 

 

Air Sampling


To assess airborne levels of mold spores, Air-O-Cell ® Cassettes and/or Anderson sampling are commonly used. Air-O-Cell ® Cassettes are a form of non-culturable sampling that quantifies the number of viable and non-viable mold spores in the air. The samples are taken by pulling a calibrated amount of air (15.0 liters/minute) through the cassette. In the cassette, air passes over a microscope slide, causing the particulates (mold spores, etc.) to stick. The slide is then examined by an American Industrial Hygiene Association (AIHA) accredited laboratory to determine the genera of mold spores present.


Anderson sampling, also known as viable impaction, allows for the speciation of viable mold spores. Sampling is performed by pulling a calibrated amount of air (28.3 liters/minute) through an Anderson Sampler and onto a Petri plate. The Petri plates are then sent to an AIHA accredited laboratory for incubation and analysis.

All air samples are taken with a Gast ® Pump (Model: R-G557X) equipped with a rotameter. Before sampling begins, the pump is calibrated with a Bios DryCal ® DC-Lite Primary Flow Meter (Model: H) to the appropriate flow rate. Samples are taken at an approximate height or four (4) feet.

All indoor air samples are compared to an outdoor reference to determine if elevated spore counts are present. As a general rule of thumb, the genus of fungi collected from indoor air should match outdoor air and be present at equal or lower levels. In some cases, outdoor air may not be a reliable baseline reading. This occurs when fungi are at extremely low levels (e.g. snow cover, rain, frost, etc.). In these cases, an ‘area of non-concern’ or EMLAB’s Extended Outdoor Comparison will be used.

 


Surface Sampling


Surface samples (swab or tape lift) are used to identify visible mold growth. A swab sample can either be transferred to a microscope slide for microscopic examination, or to a Petri plate for speciation. Tape lift samples are examined directly with a microscope to identify the genera of mold present. Speciation cannot be determined from a tape lift sample.



Bulk Sampling


A bulk sample of a building material, such as insulation, can be taken for analysis. Typically, the mold spores are isolated from the material and identified by microscopic examination.

 

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ZWS Environmental Services, Inc.

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Appleton, WI 54913

 

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Email: bill@zwsinc.com

 

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