Indoor dampness levels were recorded at a level of 10-50%, prevalent in office buildings, day cares, and schools. High humidity, condensation, and water damage, either past or present, promote the survival and growth of fungi which result in higher exposure to fungal allegens, toxins, and irritants. These damp environments also cause bacteria endotoxins. The damp materials also increase their chemical degradation resulting in more emissions of volatile organic compounds, such as formaldehyde.
More Information available at World Health Organization.