Over the past several years, the awareness of mold and indoor air quality have become a primary focus. Investigation and remediation of water leaks, chemical use, building renovations, floods, and fires have greatly expanded to include indoor air analysis. Investigations typically include visual inspection of the accessible areas in order to identify the presence of any potential contaminant sources, including volatile organic chemicals and microbiological contamination. Following the visual assessment, the collection of air and wipe samples are performed for various laboratory analysis. These measurements provide an assessment of possible contaminants at the site which includes the enumeration and identification of mold genera. Observations will also focus on potential moisture issues and related mold bacteria growth.
General Summary of Microbial Guidelines
There are few government standards currently in effect for microbiological contaminants. There exist several non-regulatory guidelines (listed below), which are based on field experience. It must be emphasized that fungal and bacterial contamination is a dynamic phenomenon and that species within an area can change due to environmental conditions. In addition, sensitivity to microbes varies from person to person.
|Parameter||Target Level||Agency or Organization|
|Fungi (species occurrence)||No confirmed presence1 of Stachybotrys
chartarum, Aspergillus versicolor, Aspergillus fumigatus, Aspergillus flavus
and/or Fusarium moniliforme
|Fungi (species comparison)||Indoor samples are not dominated by species that are not found outdoors||AIHA|
|Fungi (density comparison)||Not significantly greater than outdoor air concentrations||ACGIH3 and AIHA|
1 Confirmed presence means colonies in many samples or many colonies in any one sample.
One colony in one or two samples does not constitute “confirmed presence”
2 American Industrial Hygiene Association
3 American Conference of Governmental Industrial Hygienists
4 For Viable air samples
Air samples for microorganisms are generally evaluated by comparing indoor concentrations to ambient outdoors conditions or a control sample. Significantly elevated indoor concentrations and/or identification of different species in comparison to the control sample suggest the existence of microbial amplification sites. Non-viable spore counts include all spores, with no differentiation of viability, observed by the microscopist during sample evaluation. When analyzing viable spore samples, the sampling media is incubated for a certain period and then analyzed. This allows for the analysis of only those spores that are viable.
Following the investigations, we typically prepare a letter report presenting the results of the tests, and our observations. If appropriate, recommendations for mitigation action and/or additional investigation are provided.