A method to determine the rate of local transport into the indoor air of a substance originating from the construction frame of a building has been devised and tested. In particular we demonstrate that a tracer located outside the air and vapour barrier in the construction frame of an office building can be detected in varying concentrations in the office indoor air. The tracer may either diffuse directly or follow with outside air leaking through the barrier. Cor-recting for the local air change rate yields an apparent emission rate as an estimate of the rate of local transport from the construction frame to the indoor air. Our interpretation is that high-er apparent emission rates predominantly reflect higher local air leakage rates through the air and vapor barrier. This information could be useful for interpreting office worker complaints and for decisions on renovation options. The tracer techniques used in the study are also more generally applicable to convert measured concentrations of indoor substances into apparent emission rates. Emission rates are more indicative of the location of pollution sources and may therefore be useful in other investigations of polluted buildings.