Efficiency of ventilation in office buildings.

lnadequate ventilation is often cited as the cause of unhealthy air quality within office buildings, whilst excessive ventilation is similarly assumed to be the cause of discomfort and energy waste. However, the reality is that very little data is available to assess the significance of these problems on any large scale. The perfuorocarbon tracer (PFT) technique offers the potential for overcoming the problems of applying conventional tracer gas techniques to large or multi-roomed buildings. Methodologies are described for its application to measure ventilation in a selection of different office building types, based on the concept of homogeneous tracer gas emission. Local ventilation rates are measured in a multicell office building, with both mechanical and natural ventilation. These illustrate the distribution of ventilation and highlight implications for air quality and energyefficiency. A multicell computer model is used to validate the field protocol and to compare predictions with measured results. A simplified PFT measurement system based on standard commercial equipment is described, to encourage wider use of the method.