Review of literature indicates that methods of assessing indoor air quality are not readily available. From theoretical considerations, a practical procedure for evaluating indoor air quality in buildings is proposed. This procedure is suitable for generalized surveys of buildings where no prior knowledge of indoor air quality problems exists. The procedure is intended to indicate whether or not a more detailed analysis is necessary;The procedure consists of two main steps: first, a multipoint tracer gas analysis is performed to characterize air exchange rates and ventilation efficiencies in various zones of a building; second, the factors which influence indoor air quality are measured at the zone where they are generated and in the zone with both the lowest air exchange rate and ventilation efficiency;A model is presented which validates the correctness of the choice of the sampling locations. The Relative Exposure Index, the main concept of this model, is introduced and its relationship to the concepts of air exchange rate and ventilation efficiency is presented. Results of controlled experiments and field studies to validate the model are presented;It is concluded that there is a need to monitor contaminants at more than just the zone where contaminants are produced if the highest-risk for the occupants of the building is to be found; that most rooms in a building can be considered to be uniformly mixed; and that measuring air exchange rates using artificial mixing via a central air fan or portable fans is not an appropriate means to assess indoor air quality in buildings.