Moulds are microscopic fungi that live on organic matter. They produce spores which can be air-borne, water-borne or insect-borne and are highly adapted to grow and rapidly reproduce under the right conditions. The 3 primary conditions mould spores require to grow are a warm environment (47-120 degrees F), nutrients (something to eat- organic matter) and moisture/water. A warm environment and nutrients are part of most indoor spaces. However, when there is excessive moisture mould will thrive.