Emission of volatile organic compounds (VOCs) from materials is traditionally determined from tests carried out in small-scale test chambers. Howeyer, a difference in scale may lead to a difference in the measured emission rate in a small-scale test chamber and the actual emission rate in a full-scale ventilated room when the emission is fully or partly evaporation controlled. The objective of the present research work has been to investigate the change of emission rates from small-scale experiments to full-scale ventilated rooms and to investigate the influence of the local air velocity field near the source. A series of CFD experiments has been carried out for different set-ups and different air change rates. The results provide a method to compare mass transfer coefficients found in different scales and different geometries for evaporation controlled emission processes. Furthermore, the results show that for a given set-up the mass transfer coefficient increases with velocity and turbulence intensity.