Post Remediation Clearence Criteria

We have developed Post-Remediation Evaluation Criteria for Mold Contamination, based on non-cultured sampling. All the procedures have been laid out for a post-remediation evaluation in a six-step chart.

To start, a visual inspection is conducted prior to the collection of any samples. The visual inspection is conducted to determine if the project specifications were followed, the moisture source was identified and corrected, and that the work area is dust free (white glove test). Only after the area passes a visual inspection are non-cultured samples collected.

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Initial interpretation of the sample data compares the total fungal spore concentration to the set number of 2,000 spore counts per cubic meter of air (c/m3) . Several studies agree that this value is typical of an environment that is not impacted by adverse interior fungal growth, in essence, a "normal fungal ecology". The data also shows that very low total counts are possible based on seasonal variability or location. Our experience is consistent with that expressed by many other authors: when comparing samples from various areas the reliability of a gross comparison (i.e., total fungal spores) drops off considerably at low spore concentrations. Therefore, an exemption from step 3 is provided for samples from inside the contained area that have a total spore concentration of less than 800 c/m3.

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The evaluation of the remediation process continues with a comparison of the total spore count inside the work area to the total spore count in the makeup air source, based on the location of the containment entry point.

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Subsequently, a rank/order comparison of the fungal types (to the genus level only) and concentrations, including hyphal fragments inside the work area, are compared to the types and amounts naturally occurring in the comparison sample. At this point, we also recommend that the levels of hyphal fragments be reviewed. Hyphal fragment is a term that many laboratories use to describe fragments of fungal organisms that are not spores. Since hyphal fragments generally do not have enough characteristics to allow them to be correlated with a specific genus of fungi, they are recorded as a separate item. Our experience indicates that when concentrations of hyphal fragments found inside are higher than those found out-of-doors, an indoor source of fungal growth is usually present. As such, we have included this secondary comparison in step 4.

The levels of fungal spores and hyphal fragments recovered in the work area sample(s) must be not more than 100 c/m3 higher than the levels of corresponding fungal spores or hyphal fragments in the comparison sample. This limit is based on the principle that all analytical methods have a limit of detection that must accommodate the limitations of the equipment used in the laboratory and for sample collection. In an indoor environment with a normal fungal ecology the ranking of the spores types found inside the work area should reflect the ranking of the comparison sample. For example, if Cladosporium was the most common spore type identified in the comparison sample, one would expect to find Cladosporium as the top ranking spore type inside the work area, only at a significantly lower level.

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At this point in the process, indicator fungal types are considered. Fungal types are designated as "indicator" if they are associated with water damage to building or indoor finish materials. Keep in mind that these fungi may also come from out-of-doors and make up a natural part of the existing flora. While several molds are discussed as potential indicators of water-damaged environments, Aspergillus/Penicillium types are mentioned frequently.

Aspergillus and Penicillium spores are lumped together when analysis is performed by direct microscopy because the spores are indistinguishable from one another. Oddly, this turns out to be a benefit for the post-remediation evaluation process. Certain species of both Aspergillus and Penicillium are early colonizers of water-damaged materials that grow quickly and disperse many spores. When these growth properties are matched with the negative health effects associated with these spores, their value as an indication of acceptable mold remediation procedures is enhanced. Our experience at Caltex International ltd with post-remediation criteria ahave led us to conservative but achievable criteria that indicator fungal types (e.g., Aspergillus/Penicillium) must be recovered at levels below 200 c/m3.

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The final step in evaluating a mold remediation project is to consider target organisms. Target organisms are identified by their characteristic need for high moisture content and/or water activity to grow, their ability to naturally produce toxins, and their common degradation of cellulose-containing materials. Spores from these target organisms are not typically found in clean indoor environments so the criterion for target organisms is zero tolerance. The presence of target organisms in a cleaned work area indicates ineffective remediation and can result in continued issues with the structure or ill-health effects for the occupants of the space.

Any time one of the steps in the evaluation process exceeds the criteria, the area must be recleaned and retested as many times and as thoroughly as needed to meet the criteria for that step before moving on to the next step. When the work area has met the criteria in all six steps, it is considered to be clean with a normal fungal ecology, and the project has been successfully completed.