The sampling process of a model room with a suction nozzle in a calm or low movement environment was numerically simulated and experimentally analyzed. Computational fluid dynamics (CFD) software. Fluent (Fluent Inc.), was used for the numerical simulation. The flow was considered to be compressible and turbulent, and particles were considered to be spheres of common density. A good agreement was found between the numerical and experimental results (maximum difference of 15% in the overlapping zone), and the numerical model was further extended and used for parametric analysis. The influence of sampling velocity and shape of the suction nozzle on sampling efficiency was investigated experimentally and numerically in a particle size range of 2-45 mum. It was found that sampling efficiency is smaller for V-shaped nozzles, mainly for lower velocities. Sampling efficiency was calculated for each particle diameter and for the whole particle size distribution as well. Sampling efficiency decreases as particle size increases. It is concluded that knowledge of sampling efficiency for each of the sampled particle sizes may indicate the concentration and size distribution in the sampled space.