The term sick building syndrome is used to describe situations in which a substantial proportion of occupants experience non-specific health and comfort effects. The complaints may be localized or widespread throughout the unit. Sick building syndrome symptoms commonly include complaints such as headache and fatigue. Symptoms quickly subside when occupants leave the building. Some investigators have attributed mold exposure as a cause, but many other sources of etiology have also been put forth. Another term, building-related illness, is a well-defined term that has a specific cause (for example, Legionnaires disease). On the other hand, sick building syndrome is a vague term that is poorly defined.