The aim is to add an optimized mouth-nose protection (hereinafter referred to as mask in simplified form) to the product (in particular a mask frame), which does not run the risk of aerosols escaping backwards due to leakage on the face, thus negating the protective effect. By means of fluid-dynamic calculations, the dispersion of the breathing air and the aerosols contained therein (water droplets, possibly with viruses) is calculated for different mask geometries. The calculations depend on the droplet size, as this has a significant influence: Large droplets are well retained by the mask or fall quickly to the ground, while small ones stay in the air for a long time. The evaporation of water in flight and the associated reduction in size also plays an important role.  Medical reliability is guaranteed by research with regard to head shape, breathing air volume and droplet sizes relevant for virus transmission. Based on these findings, mask temples are designed and printed. Covered with a suitable filter material, they will be reusable or recyclable. Masks are developed specifically for the consumer market and for the professional sector (e.g. for different types of printers).  Currently, the discussion about the effectiveness of consumer mouth and nose protection is very controversial. Therefore, reliable data on aerosol dispersal is a fundamental necessity for the production of effective masks that provide real, not deceptive, safety. With the simulation-based approach, further questions can be answered that contribute to a safe public life and thus also to a fast regeneration of the economy. These include the necessary distance of people with and without masks and the spread of infectious aerosols outdoors, in offices and in shops.