How mould travels through your home

Spores are everywhere

Mould reproduces with microscopic spores that are a normal part of the air, inside and outside every home. They only become a problem when they land somewhere with a food source (timber, plasterboard, paper, dust), the right temperature and, most importantly, moisture that isn't under control.

1. Moving air

Air movement is the main way spores and fragments travel. Air moves through planned openings such as doors and windows, and through unplanned ones such as cracks and gaps in the building.

Pointing a pedestal fan or air mover at a mouldy area can turn a room into a spore distribution system. If you suspect mould, keep fans off and away from it.

2. Air conditioning and heating

If an air conditioning or heating system becomes contaminated, it can carry spores and fragments through the whole building. Standard household filters usually aren't fine enough to stop them recirculating.

The industry standard describes this spread in conditions. Where mould is actually growing is Condition 3. Areas where spores and fragments have travelled and settled are Condition 2, even if they look clean. Normal background levels, like you would find anywhere, are Condition 1.

3. Cross-contamination

Spores also hitch a ride. Walking from an affected room into a clean one can carry them on clothes, shoes, tools and hands. Moving furniture or belongings out of an affected room without wrapping them can take the problem with them.

What this means for you

• Don't disturb visible mould with brushes, dry cloths or a vacuum without a HEPA filter.
• Keep fans and air movers away from affected areas.
• Close the door to an affected room where you can.
• Remember the moisture: mould can return wherever things stay damp.