CMI Mold Identification & Sampling Techniques 2 — Questions and Answers
Question 1: Which mold genus is most commonly associated with water-damaged gypsum wallboard and appears as a powdery white-to-gray growth?
- Stachybotrys chartarum
- Ulocladium species
- Chaetomium globosum (Correct answer)
- Aspergillus versicolor
Correct answer: Chaetomium globosum
Chaetomium globosum is a cellulolytic fungus that colonizes water-damaged gypsum wallboard, producing characteristic white-to-gray powdery growth from its perithecia. Stachybotrys chartarum also grows on wet cellulose but appears as a slimy black colony, not powdery. Ulocladium and Aspergillus versicolor can appear on damp materials but are not the primary genus associated with this specific appearance on gypsum board.
Question 2: When collecting a bulk sample from a suspect mold colony, what is the recommended minimum sample size to ensure adequate laboratory analysis?
- 1–5 mg of material
- 50–100 mg of material (Correct answer)
- 200–500 mg of material
- At least 1 gram of material
Correct answer: 50–100 mg of material
A 50–100 mg bulk sample provides sufficient material for laboratory preparation, including culture plating and direct microscopy, without requiring excessive sampling. Smaller amounts like 1–5 mg are often insufficient for reliable extraction and analysis. Larger amounts (200–500 mg or 1 gram) exceed what is necessary and can be unnecessarily destructive to building materials during sampling.
Question 3: A swab sample collected from a non-porous surface such as HVAC coil is best analyzed by which laboratory method?
- Direct microscopy (tape lift protocol)
- Culture analysis for viable spore count (Correct answer)
- Enzyme-linked immunosorbent assay (ELISA)
- X-ray diffraction spectrometry
Correct answer: Culture analysis for viable spore count
Culture analysis grows viable (living) spores on agar media, making it the preferred method for non-porous surfaces like HVAC coils where confirming active biological growth matters. Direct microscopy via tape lift works best on dry porous surfaces and cannot determine viability. ELISA detects specific antigens or mycotoxins, not general spore identification, and X-ray diffraction is used for mineral/crystal analysis, not biological sampling.
Question 4: Air-O-Cell cassettes used in spore trap sampling capture particles in what approximate size range that is most relevant to fungal spores?
- 0.1–0.5 microns
- 1–100 microns (Correct answer)
- 200–500 microns
- Over 500 microns
Correct answer: 1–100 microns
Air-O-Cell spore trap cassettes are designed to capture particles in the 1–100 micron range, which encompasses the vast majority of fungal spores found in indoor environments. Sub-micron particles (0.1–0.5 µm) are too small to be fungal spores and represent bacteria or ultrafine particles. Particles above 200 µm are too large to remain airborne for sampling and fall out quickly due to gravity.
Question 5: When performing a visual inspection, which condition is the strongest indicator that Stachybotrys chartarum may be present?
- Dry, dusty surfaces with no visible discoloration
- Chronically wet cellulose material with black slimy growth (Correct answer)
- Yellow staining on vinyl flooring
- White efflorescence on concrete block walls
Correct answer: Chronically wet cellulose material with black slimy growth
Stachybotrys chartarum requires chronically wet cellulose-based materials (such as paper-faced drywall or ceiling tiles) and produces a characteristic slimy black growth due to its mucilaginous spore heads. Dry dusty surfaces cannot support Stachy growth as it requires very high, sustained moisture. Yellow staining on vinyl and white efflorescence on concrete are abiotic (non-biological) processes unrelated to Stachybotrys.
Question 6: An inspector finds a greenish-blue powdery growth on citrus fruit stored in a basement. This is most likely which genus?
- Cladosporium
- Penicillium (Correct answer)
- Fusarium
- Alternaria
Correct answer: Penicillium
Penicillium species are the classic cause of blue-green powdery mold on citrus fruits and other food items, named for their brush-like (penicillus) conidiophore structure. Cladosporium tends to appear olive-green to black and is more common on building materials. Fusarium and Alternaria are typically found on plant material in soil or outdoor environments and do not commonly produce the blue-green powdery appearance seen on stored citrus.
CMI Mold Identification & Sampling Techniques 2
Which mold genus is most commonly associated with water-damaged gypsum wallboard and appears as a powdery white-to-gray growth?