Water intrusion should be prevented. Roofing or other facility materials should be repaired or replaced as necessary to prevent rainwater intrusion into the facility. In areas that exhibit stained ceiling tiles, the roof should be checked for leaks, and the HVAC system duct work should be checked for condensation.

All ventilation systems shall be designed and maintained to minimize or eliminate standing or stagnant water. Air handling unit condensation pans shall be designed for self-drainage to preclude the buildup microbial growth and oxidation of the metal pan. The continual use of biocides in condensation pans is generally not recommended due to the potential for corrosion of ventilation system components and/or adverse facility occupant reactions to the biocide.

All visible microbial contamination in ductwork, humidifiers, other HVAC and facility system components, or on facility surfaces should be removed. Any use of biocides on existing microbial contamination within a ventilation system must be performed in a safe manner without releasing biocide material into occupied spaces. Cooling coils and condensate pans should be periodically cleaned with an anti-microbial agent.

If the relative humidity in occupied spaces and low velocity ducts and plenums exceeds 50%, fungal contamination (i.e., molds, mildew, and other fungi) can occur.