The detailed flow behaviour around a special purpose four-hole Cobra Pilot pressure probe with purging is investigated computationally in gas and gas-particle flows. The incompressible steady state Navier-Stokes equations for the gas phase are solved numerically using a general purpose computational fluid dynamics code. Computational results are presented at a typical Reynolds number of 2 × 103. The use of purging gas blown out of the pressure ports to prevent particle blockage is modelled, providing design and operational data: (1) on the effects of purging gas on the calibration characteristics of the probe, and (2) the effectiveness of purging on particle blockage prevention. A Lagrangian procedure is used to calculate the particle trajectories via a one way coupling formulation. A continuous purging velocity of 30% of the freestream velocity prevents blockage by solid particles and allows a monotonic calibration to be maintained.