Penicillium
RoutinePenicillium species
Penicillium is the mould on forgotten bread and the source of penicillin. Indoors it colonises damp carpet, wallpaper, insulation and soft furnishings quickly after a water event, and it is a major contributor to the musty smell people associate with damp houses. It is a common allergen and a routine remediation.
Quick facts
- Appearance
- Blue-green or grey-green powdery colonies with a characteristic white fringe at the growing edge, and a texture like fine felt. On food it is the familiar blue-green fuzz on bread and citrus.
- Moisture
- Grows on humidity alone — no leak needed
- Smell
- Distinctly musty — this genus is responsible for much of the classic 'damp' smell.
- Colours
- green, blue, white
- Texture
- powdery, velvety
- Surfaces
- food, drywall, fabric, wood
How to recognise it
- Blue-green colour with a white growing edge.
- Powdery, felt-like texture.
- Strongly associated with the musty damp smell.
- Colonises water-damaged materials within a couple of days.
What it tells you about the building
Recent or ongoing water damage, or humidity high enough to keep soft materials damp. Materials that have been wet for more than 48 hours generally need replacing rather than cleaning.
What it gets confused with
One observation settles each of these.
Not reliably separable without a microscope. Both are treated the same way.
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.