The aim of this research is to understand how mid-latitude weather systems ventilate pollutants out of the boundary layer. Specifically, which regions of the boundary layer beneath mid-latitude weather systems can exchange air with the troposphere which physical processes act to transport pollutants, and what controls the amount of ventilation. These questions are investigated by simulating dry baroclinic life cycles in the presence of a boundary-layer parameterisation scheme with a passive tracer included to represent pollutants.