Devolatilization is a key step in polymer processing. Low-molecular-weight components are removed from a polymeric system. The transport of these components takes place by diffusion to the polymer-vapor interface. This interface can be formed by free surfaces of single-phase polymer melts or by bubbles. In this study the transport with and without bubble nucleation is investigated independently from each other in a specially designed apparatus. The mass transport in thin films and in rotating pools with surface renewal is measured. High surface renewal rates and thick films enhance the mass transfer for single phase flow. For two phase flow and devolatilization the conditions for bubble nucleation and foam formation are investigated. The bubble nucleation is observed in the rotating pool in the area of high shear velocity.