To investigate the levels of protection, and their variation, wearing of face masks could convey to untrained subjects we designed a study in which healthy volunteers would be wearing different types of professional and home-made masks during a selection of activities, in different conditions (inward protection). We also assessed the protection different types of masks could convey when worn by a simulated infectious patient (outward protection). Resulting quantitative descriptions of distributions of protection factors may be used for assessing the importance of mask use in respiratory disease transmission.