Any type of water intrusion into a given indoor environment has the potential for causing magnification of fungus growth. Fungi thrive in environments with little ventilation and large quantities of no moisture control and organic material. Water, on the other hand, is not always readily available in large quantities, particularly in indoor environments generally inhabited by people. Water intrusion into any given environment is, therefore, the single most important cause of fungus contamination.
Some fungi are toxic to humans.
Toxic fungi produce metabolites known as mycotoxins which may have a variety of toxic effects when inhaled, ingested, or when they come into contact with skin. However, all fungi, regardless of toxin producing capabilities, can cause allergic respiratory disease in sensitive individuals. The types of disease that can be caused by fungi in sensitive individuals include humidifier fever, hypersensitivity pneumonities, asthma, and allergic rhinitis. Another significant problem posed by magnification of fungus growth is the damage to wood structures that is caused by some species of wood destroying fungi. This type of damage is particularly insidious since it can go undetected for long period of time resulting in unexpected structural failure and potential injury to building occupants.