How big of a concern is mold for indoor spaces in buildings? Mold is one of the most pervasive hidden dangers to indoor air quality (IAQ) and occupant health in a building environment. About 80% of the Industrial Hygiene issues we deal with in buildings are due to mold. People erroneously assume that mold is only a concern in humid climates during the warm summer months, but the root cause of mold in a building is any kind of water intrusion and trapped moisture generally coupled with poor ventilation. Going into the winter months, this can happen due to heavy rain and snow, which can intrude buildings through penetrations, improper drainage, leaky roofing, and other structural concerns. Why is mold such a hidden danger? One of the challenges is that mold growth is often not detected until it becomes a serious issue. Mold colonies can start behind exterior walls, behind wall boards, in attics and in roofing insulation, in as little as 24 to 48 hours after water exposure. By the time it is detected, it’s usually in the form of poor IAQ – unpleasant moldy odors, allergies, sick occupants. In severe cases, tenants may be displaced or need relocation, which could result in expense or loss of revenue for all. What other risk factors in buildings can result in mold? Mold spores are ever-present in our environment, and therefore can grow in and on any porous building materials under moist conditions. Additional risk factors can include poor ventilation, leaky plumbing, areas of the building (or entire buildings) that are closed up for some period of time, and improper insulation from outdoor weather.