During September and October, 1998, the new Integrated Organic Gas and Particle Sampler (IOGAPS), was operated at Hazelrigg, UK, the field measurement station of the University of Lancaster. Gas/particle partition ratios of twenty-two 2–5 ring PAH were determined using both the IOGAPS (in which the gas phase is collected before the particle phase) and a low flow sampler which utilized the traditional filter-sorbent geometry. For compounds of intermediate volatility, less partitioning to the gas phase was observed when the denuder was used. The denuder (8- channel, 60 cm, 16.7 L min−1 air sampling rate) trapped small amounts of several non-volatile PAH. This result is consistent with particle diffusion losses of 5 to 10% for particles less than 0.05 μm under the flow conditions in the denuder. The 60-cm denuder was probably longer than necessary for the flow rate used. During the sampling, both glass fiber and Teflon-coated glass fiber filters were used. Without a denuder in front of a glass fiber filter, the fine particulate mass (PM 2.5) measurements showed a major positive bias that has been attributed to adsorption of gases by the filter. Teflon-coated glass fiber filters were not subject to this artifact problem, and equal masses were collected on filters from the denuded and non-denuded air flows.