Mold Growth

Places to Find Mold Growth

Look especially for black, grey-brown, grey-green or pink mold areas. Gently pull back rippled, water damaged wallpaper or wallboard paper in order to look at what molds may be underneath. If ducts are suspect, dab a little sticky tape into their interiors to sample the materials adhering to their surfaces. When you find suspected mold growth, impress it onto sticky tape (cellulose-acetate, e.g., Scotch brand) and examine it under the microscope. Under the microscope, make sure you see not just conspicuous dark conidial types but also less conspicuous hyaline conidia, especially small, roundish conidia, or fungal spores, in chains, signifying the presence of Penicillium or Aspergillus. Look also for arthropods, their exoskeletal fragments, and their faecal pellets. Fungivorous (fungus-eating) mite pellets are rounded and usually full of conidia. Booklouse, beetle and millipede feces, at least when found in mold infestations, resemble short, broken cylindrical columns composed of masses of conidia. Sometimes arthropod pellets will contain interesting mold elements not seen directly on the material sampled. For example, a health inspector recently sent me a tape impression from fiberglass insulation-covering paper in a house with problematic leaks. The paper surface itself had only a little Cladosporium on it, but booklouse and mite feces scattered here and there were full of Stachybotrys conidia. Evidently there was a great deal of Stachybotrys within easy mite walking distance (i.e., within a few inches), most likely on the interior surface of the same paper. There were probably some minute cracks that the animals used to go back and forth from one side of the paper to the other.

If there are continued complaints and mustiness but no mold is found, consider whether or not there are any clues to where hidden mold may be. If building occupants remember a substantial leak or flood (or similar incident, e.g., fire extinguished with water) in a certain area, consider inspecting the wall, ceiling or floor interior at that place. The exterior of the damaged area may have been superficially repaired, leaving all the interior problems intact. Take out a ceiling tile or cut a four- to eight-inch inspection port into the suspect area. The same may be done in areas where wallboard or ceiling tiles have become watermarked but the exterior is not actually moldy. The interior space, which forms a sheltered humid chamber facilitating fungal proliferation, as well as a conduit for leaks, is far more likely to be grossly moldy than the exposed exterior is. There is actually plenty of airflow between wall and ceiling/floor interiors and the inhabited parts of rooms, especially at the joins, so molds inside structural interior spaces are frequently sources of problems for building occupants.

If there is no strong clue to where mold may be, this is the best time to try air sampling. Analyze culture plates or strips in comparison to an outdoor air control to determine if there is an unusual mold buildup in the building. If there is, look up the mold's general habitat characters in a reference work such as the Compendium of soil fungi.

Use the information given as a clue to what sort of indoor microhabitat you will find the mold growing in. It is best to use a medium such as DG18 (dichloran 18% glycerol) that both osmotolerant fungi (drought-tolerating fungi such as Aspergillus glaucus) and mesophilic fungi (fungi such as Stachybotrys requiring high moisture levels) are known to grow on. In addition to viable air sampling, non-viable air sampling may be used (e.g., Rotorod). It will detect significant dead elements such as effete Stachybotrys conidia. An alternative to this non-viable air sampling is direct microscopy of settled dust, e.g., from shelf surfaces. Dust from floors that are frequently walked on with shod feet may be difficult to analyze because of the deposition of outdoor mold spore elements. Be aware that old library books may exude a musty odor which in my experience often seems not to be significantly associated with molds. Anyone who can tell me what this odor derives from will have my undying gratitude. I assume it may have something to do with the inherent self-destructiveness of modern acid papers. Library staff may find it quite oppressive and call in fungal analysts.