Summary: The COVID-19 pandemic has caused a strong increase in the demand for face masks. In response to existing shortages, many public health institutions have recommended home-made cotton masks as an acceptable alternative to the N80, N95, and N98 respirators and/or surgical masks. While mask wearing is primarily intended to protect others from exhaled respiratory droplets containing viruses, relatively few studies have looked at the emission of particles by mask wearers to the environment. Both surgical masks and KN95 non-ventilated respirators reduce the emission of particulate matter to the outside by 90% and 74%, respectively, when talking and coughing, compared to walking without a mask, confirming their effectiveness in reducing emissions to the outside. Fur-ther studies are needed to establish the effectiveness of cloth masks in blocking exhaled particles in speech and coughing with varying intensity, and to carefully assess whether viral-contaminated fabrics can mediate their further transmission, but results so far strongly indicate the effectiveness of medical masks/respirators and emphasize the importance of regular hygiene of homemade cotton masks.