Aspergillus species
The most common genus in water-damaged building assessments
What it tells you about the building
Aspergillus species are xerotolerant — several thrive at lower moisture levels than most molds, which lets them colonize buildings from humidity alone with no leak anywhere. This makes the genus the workhorse finding in chronically humid homes, HVAC systems, and below-grade spaces.
Why it matters in assessments
Several Aspergillus species (including A. versicolor and A. penicillioides) are core water-damage markers in qPCR dust indices. Because the genus spans many species with different implications, species-level identification from DNA-based testing is far more informative than a genus-level microscopy call.
What remediation requires
Because humidity alone sustains it, remediation must include environmental control: dehumidification to the 35–50% band and HVAC assessment alongside removal of colonized materials and fine cleaning. Killing surface growth while leaving humidity high guarantees recolonization.
Highly variable by species: powdery colonies in green, yellow, brown, or black, often blending into dust rather than forming dramatic patches.
- Damp drywall and wood
- HVAC systems and duct dust
- Carpets and mattresses in humid rooms
- Stored fabrics, leather, and paper
State editions
Where this species shows up depends on where local climate and housing stock meet its moisture requirement. Read the local picture:
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