In most countries in the world facemasks are used by the public during the COVID-19 pandemic. There are also scientific reports that suggest that this tactic will slow down the spread of virus. At the same time some governments, especially in the Nordic countries, hesitate and people do not generally wear facemasks. One reason for this large difference is that the mechanism behind the spread of fluid particles of different size, in different environments and when people are wearing facemasks or not, is not known to any large extent. Hence, by using modern numerical and experimental tools within the area of fluid mechanics we aim to gain insights on such multiphase flows and deliver guidelines of the use of facemasks to prevent spreading of virus including COVID-19. Researchers from four major academic institutions in Sweden (CTH, KTH, LTH and LTU) will work together with tools available at respective university, such as Computational Fluid Dynamics and Lattice Boltzmann codes and experimental set-ups with the Schlieren technique, Particle Image Velocimetry and Holographic methods.