How do I know if mold testing in my house is done right?-Barbara 

            Last week, the use of culturable/viable sampling methods, their advantages and disadvantages were discussed.  They are best used in conjunction with other types of sampling.  The use of total mold spore sampling in conjunction with culturable/viable sampling is recommended.

            In total mold spore sampling, air is drawn into a sampling device that impacts airborne particles (including mold spores) onto a greased microscope slide or coverslip.  Mold spores and other mold particles collected are counted on high power (1000X) microscope and concentrations expressed as spores per cubic meter (S/m³). 

            Total mold spore counts include both viable and non-viable spores/particles.  As a consequence total mold spore counts are commonly 10-15 times higher than concentrations determined from culturable/viable sampling.  In my own testing experience, total mold spore concentrations have varied from as low as twice as high to over 200,000 times higher. 

            The ratio of concentrations of these two techniques is an important tool in interpreting results.  A low ratio (e.g. 2 to 4X) indicates a relatively active mold infestation and/or release of mold spores.  A high ratio indicates that the infestation is older/less active or that some factor in the environment is causing mold spores to rapidly lose their viability. 

            Based on my own experience, a total mold spore count of 10-15,000 S/m³ is indicative of a mold infestation/exposure problem in a residence. In problem environments, concentrations in excess of 20,000 S/m³ are not uncommon; in worst case environments >1 million S/m³. 

            Total mold spore sampling has the advantage of collecting most airborne spores that are drawn into the collector.  Since allergenicity is independent of viability, results from this method are in most cases a much better indicator of health risks than the culturable/viable method.  Though many mold spores can be identified to genus from their spores, this technique does not allow one to identify mold types to species.  This is its major limitation. 

            The total mold spore sampling method has other advantages that have greatly increased their use in the past two years.  Most notable is the use of this method for clearance sampling after a Stachybotrys remediation (as well as other mold remedations) and to sample mold in wall cavities using the Air-O Cell cassette. 

            Three different total mold samplers are used by mold investigators.  These include Burkard, Allergenco and Air-O-Cell samplers. Llaboratory calibrated Burkard , Allergenco  and Air-O-Cell samplers used with 1000X magnification provide excellent results. These results are significantly compromised when analysis is conducted at 400X magnification as is the case with a number of laboratories. The Air-O-Cell cassette has one major advantage; it can be used to determine the presence of Stachybotrys and other mold species inside wall cavities.