Inclusion Criteria:  people familiar with the use of face masks, absence of allergy or intolerance to sodium saccharin or materials used, absence of relevant systemic diseases, age between 18-65 years, absence of obvious facial hair and signing the informed consent.  Exclusion Criteria:  people not familiar with the use of face masks, presence of allergy or intolerance to sodium saccharin or materials used, presence of relevant systemic diseases, presence of obvious facial hair and not signing the informed consent.