Six Principles of Indoor Mold Growth

Mold is everywhere
Molds are naturally occurring and widespread in the environment. It is not possible to eliminate exposures to all molds, nor is it necessary from a health perspective.
Moisture is the key determinant of indoor mold growth.
The surfaces of most indoor environments provide appropriate temperature conditions and ample nutrients for molds to grow; water is the only additional element required for mold growth.
Mold is associated with human health effects,
Dose-response relationships between the amount of mold in an indoor environment, the species of mold, and the level of mold exposure and human health are not clearly defined.
There are no recommended health-based exposure limits for mold.
Due to a lack of scientific data, most professional organizations have not agreed upon or supported numerical limits for mold in residential environments.
Mold is a mixture of live and dead organisms;
Both can be harmful. Both live and dead mold and mold fragments contribute mycotoxins and other mold products, which have been shown to retain their antigenic and toxic properties over extended periods of time.
Determining mold exposure is complex.
Currently, there are no scientifically validated methods to measure mold exposure with accuracy.
Reference from The National Collaborating Centre for Environmental Health at the British Columbia Centre for Disease Control