If the fungus is already growing inside the building or ventilation system, the problem becomes somewhat more difficult. Fungi require moisture for growth. The source of the moisture must be identified and then controlled. Cooling coils, drains pans, and water pans for humidifiers are likely locations for fungal growth, especially when there is standing water. These components should be disassembled and cleaned with a strong disinfectant, such as chlorine, when fungal or bacterial growth is found.
Clogged drains are often a cause for standing water.
Condensation on ductwork or other components is another likely source of moisture. The ductwork must be inspected for fungal growth and cleaned with a disinfectant. The cause of the condensation must be identified. Often, it results from inadequate insulation, or leakage into, or out of, the ductwork. Sometimes return air can leak into the supply air duct and result in localized condensation.