In most modern buildings environmental conditions which have significant effects on human comfort, such as temperature, ventilation, and, in some cases, relative humidity, are mechanically controlled by a variety of environmental/climate control systems. Environmental conditions extant in building spaces at any given moment are a product of a number of physical factors. These include temperature, relative humidity, air movement, ventilation, lighting, noise, vibration, and a variety of electrical and magnetic phenomena. In addition to heating, and in many cases cooling, environmental systems are often designed and operated to provide outdoor air and air circulation to dilute contaminants for the purpose of maintaining human comfort. Environmental control systems which regulate building thermal and ventilation conditions may be risk factors for problem-building complaints and Sick building syndrome (SBS) symptoms. Much of the focus of problem building investigations centers on identifying causal factors responsible for health and/or comfort concerns.