The polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants in plastics of soft furnishings, TV sets and computers, and insulation in the indoor environment. The penta-BDEsnow banned in most parts of Europe but still used in North Americaare additive flame retardants that may be released to the indoor environment via volatilization or as dusts. In this study, to investigate general population PBDE exposure, air was sampled in 74 randomly selected homes in Ottawa, Canada and at seven outdoor sites during the winter of 2002−3, using polyurethane foam (PUF) disk passive air samplers. The passive sampling rate (2.5 m3 day-1) was determined through a pilot study employing active and passive samplers side-by-side at selected indoor locations. Indoor air concentrations of PBDEs were log-normally distributed with a geometric mean of 120 pg m-3 and a median of 100 pg m-3, approximately 50 times higher than the range of outdoor air concentrations (<0.1−4.4 pg m-3). The maximum daily human exposure via the inhalation pathway based on median PBDE levels found in this survey was estimated to be 1.9 ng day-1 (female) and 2.0 ng day-1 (male), representing 4.1% (f) and 4.4% (m) of overall daily intake.