Aspergillus
InvestigateAspergillus species
Aspergillus is a very large genus, some members of which matter medically. It is a common indoor mould and a significant allergen, and a few species can cause genuine infections in people who are immunocompromised or have existing lung disease. For a healthy household it is a cleaning job; for someone on immunosuppressants or with a transplant, professional remediation is the right call.
Quick facts
- Appearance
- Powdery colonies with a granular surface, in an unusually wide colour range — green, yellow-green, white, brown or black — often with a paler edge and darker centre as the colony matures.
- Moisture
- Grows on humidity alone — no leak needed
- Smell
- Musty, sometimes sharp.
- Colours
- green, yellow, white, black, brown
- Texture
- powdery, fuzzy
- Surfaces
- drywall, food, fabric, wood
How to recognise it
- Powdery, granular surface that puffs when disturbed.
- Circular colonies with a distinct edge, often two-toned.
- Wide colour range, so colour alone will not identify it.
- Common in HVAC systems, stored food and damp building materials.
What it tells you about the building
Persistent damp. If anyone in the household is immunocompromised, has asthma or has a lung condition, this is the case where professional remediation is proportionate rather than excessive.
What it gets confused with
One observation settles each of these.
Penicillium is more typically blue-green with a white fringe. The two are genuinely hard to separate by eye and the response is identical.
Cladosporium is velvety; Aspergillus is powdery and granular.
Where it turns up
The species matters less than you think
- Public health guidance is to remove all indoor mould regardless of type. The CDC and EPA do not recommend routine species testing for ordinary households, because the response does not change: find the water, stop it, remove the growth.
- “Toxic black mould” is a marketing phrase, not a category. Stachybotrys is real and does need soaked material to grow, so finding it tells you something useful about your building. But the health effects that are well established — allergy, asthma aggravation, irritation — are not specific to it.
- Mould without water does not persist. Cleaning growth while leaving the moisture source is why it comes back. The leak, the condensation or the ventilation is the actual problem.
Call a professional for areas larger than about 10 square feet, for anything in HVAC ductwork, after sewage or flood water, or if anyone in the household is immunocompromised or has a lung condition.