Employee complaints can be due to two types of building problems: Sick Building Syndrome (SBS), and building-related illnesses. SBS is used to describe situations in which building occupants experience acute health effects that appear to be linked to time spent in a building, but no specific illness can be identified. SBS is associated with complaints of discomfort including headache, nausea and dizziness; eye, nose, throat, and respiratory irritation; coughing; difficulty concentrating; sensitivity to odors; muscle pain; and fatigue. The specific causes of the symptoms are often not known but sometimes are attributed to the effects of a combination of substances or individual susceptibility to low concentrations of contaminants. Symptoms of SBS are associated with periods of occupancy and often disappear after the worker leaves the worksite.