Real time monitoring of total volatile organic compounds (TVOC) in rooms of Japanese university buildings was carried out to understand the temporal changes in actual indoor air quality.

The TVOC concentrations in seven different rooms, consisting of a lecture room, a seminar room, three laboratories, a computer room and a library, were monitored continuously for 24 h via a personal VOC monitor equipped with a semiconductor gas sensor. An active sampling-thermal desorption method using stainless steel tubes packed with Tenax -TA was also carried out simultaneously to verify the usability of the monitor.

The TVOC concentrations measured by the personal VOC monitor were closely correlated with those measured by the active sampling method. The TVOC concentration in all rooms was generally low during the day and increased during the night. This concentration change corresponded to the ventilation cycle in the building. During the day, the TVOC concentration was generally lower than the provisional target criterion (advisable value) of indoor air quality in Japan (400 μg/m³). During the night, however, it exceeded this criterion in several rooms, especially during the summer season.

The real-time monitor using a semiconductor gas sensor can provide useful data on changes in the TVOC concentration in indoor air with high sensitivity.