Quantification of indoor TVOC levels from different sources in mechanically ventilated buildings

The levels of total volatile organic compounds (TVOCs) in 17 building premises including offices, customer services centre, social services centre and fitness facilities were measured using a real-time monitoring method by a photo-acoustic infrared instrument. Measurements were taken both when the mechanical ventilation system was operating and when it was not operating. Simple source apportionment analysis was conducted based on a simplified materials balance equation to identify sources of the indoor VOC accumulation and their contributions from building material-related sources, occupant-related sources and the outdoors. The average emission rate of TVOCs from building materials was 0.19 μg·m^-2·s^-1 and that from the occupants was 5 μg·s^-1 per person. The TVOC emission rate from ventilation ductwork was 0.21 μg·s^-1. During the daytime, the building material-related TVOC sources and the occupant-related TVOC sources each contributed 17.5 and 14.9% by weight to the total indoor TVOC accumulation, respectively, with the remaining 67.5% coming from the outdoor sources. During night-time, the building material-related TVOC sources contributed an average of 32.2% by weight to the total indoor TVOC sources and the remaining 67.8% came from the outdoor sources. The indoor TVOC level contributed by the ventilation ducting and related sources was found to be negligible.