Building related illness is a term used by the Environmental Protection Agency (EPA) when symptoms of a diagnosable illness are identified and attributed directly to air quality inside a building. Symptoms may be caused by an allergic reaction to airborne contaminants, and may include cough, chest tightness, fever, chills, and muscle aches, and do not clear up when people leave the building.

Often this condition is temporary, but some buildings have long-term problems. Frequently, problems result when a building is operated or maintained in a manner that is inconsistent with its original design or prescribed operating procedures. Sometimes indoor air problems are a result of poor building design or occupant activities. In contrast to SICK Building Syndrome.