The filtering facepiece operates through filtration without the ability to kill the viruses.
If the filtration might be combined with antiviral agents simultaneously in the masks, this would be much more efficient not only during the use of these masks but also against cross-infection after being discarded. For centuries it is well known that sodium chloride (NaCl) contributes to inhibit pathogens on various occasions. If aerosol with infectious agents reaches the surface of the filtering facepiece, coated with hypertonic saline, they become attracted by hygroscopic salt crystals. Proteins and nucleic acids lose their structural integrity and become inactivated concerning their infectious properties. We provide further evidence for cell growth inhibition with hypertonic saline in yeast cells comprising a defending cell wall. Proliferation was inhibited in a concentration-dependent manner, i.e. above 50g/L, yeast cell proliferation was completely blocked. At a NaCl concentration of 100g/L, even decomposition of the original inoculated organisms was observed. Therefore, we conclude that hypertonic saline coated filtering facepiece might strongly reduce the numbers of infectious particles on their surfaces and thus protect mask carriers efficiently from infections.
For centuries it is well known that sodium chloride contributes to germ inhibition on various occasions. For example, the Dead Sea and salt lakes contain a high concentration of sodium chloride with practically no microorganisms [Williams, 1993] .
The hypertonic environment outside the cell is responsible for water diffusion from the cell which is associated with dehydration and shrinking of the cell. This is the reason why nutritional meat gained durability if salted extensively.
A key task of hypertonic saline solution is widespread and rapid protein damage due to aggregation and misfolding of diverse proteins and loss of water [Burkewitz et al., 2011] . Not only proteins are affected by denaturation, but also nucleic acids. Virus particles consist predominantly of nucleic acids and proteins and may, therefore, be especially sensitive to hypertonic saline. If denaturated by salt, it is assumable that their surface proteins become destructured and their binding capacity to cell receptors is at least strongly reduced if not inhibited.
Lungs are marked with a large surface exposed to the external environment. 
Growth inhibition of hypertonic saline was evaluated on a robust unicellular organism with a defending cell wall i.e. in yeast (OSNA Nährmittel GmbH, Osnabrück, Germany).
In a first step a yeast suspension of 500 mg dried Saccharomyces cervisiae in 50 ml A. dest. comprising 5% saccharose (Südzucker, Mannheim, Germany) was prepared.
Microtitre wells were inoculated with 20 µl of this suspension. Thereafter 100 µl of 20% saccharose in A. dest. were aded to each well followed by 100 µl of the appropriate double concentrated salt solutions i.e. 0, 10, 25, 50 and 100 (g/L) sodium chloride (NaCl) as well as a commercially available product (MIHESA  , Omnignostica Ltd., Höflein/Danube, Austria). The mixtures were kept in humid chambers at room temperature on a rocking device. Growth curves were determined through measurement of the turbidity of each well at the beginning and after 24 hours at 650 nm. All determinations were carried out in 10-fold replicates.
After an incubation of 24 hours, we observed a complete growth inhibition above 50 g/L NaCl. Above 100 g/L NaCl lead to decreased absorption units compared to the initial ones, thus indicating a decomposition of the original yeast suspension ( figure 1 ). 
Hypertonic saline inhibited yeast cell proliferation in a dose-dependent manner. This effect was observed in a unicellular organism comprising a defending cell wall in contrast to viruses. Therefore, even speaking of COVID 19, this unspecific salt effect might not only enforce the protection of filtering facepiece but could even protect humans from this particle until an efficient vaccination is found for specific protection 