The ASHRAE definition is as follows: SICK BUILDING SYNDROME: "SBS" If more than 20 percent of the building occupants complain of such problems as headache, eye irritation, fatigue and dizziness for more than two weeks; if the symptoms are relieved when the complainant leaves the building; and, if no specific cause of the problem can be identified. (ASHRAE Journal, July 1988, p.40)