Indoor air pollutants affecting the quality of indoor air originate from indoor sources such as people, their activities, tobacco smoking, building and furnishing materials, electronic equipment and heating, ventilation and air-conditioning (HVAC) systems, as well as from outdoor sources, e.g. urban traffic. Exposure to high concentrations of indoor air pollutants have been shown to reduce the performance of diagnostic psychological tests in experiments in which subjects were exposed to toluene at 380 mg/m3

(Bælum et al., 1985) and to a mixture of 22 common indoor air pollutants at concentrations up to 25 mg/m3 (Mølhave et al., 1986). However, these studies were carried out on selected indoor air pollutants and at concentrations considerably higher than those that typically occur in office buildings (Brown et al., 1994; Wargocki, 1998). Furthermore, they used diagnostic psychological tests of short duration, which may not predict the performance of typical office work over time.