- persons with history of hypersensitivity to silver (rashes and other contraindications), - a history of sars-cov-2 infection in the three months prior to the start of the study, any respiratory distress, - and refusal to sign the informed consent.

- persons with history of hypersensitivity to silver (rashes and other contraindications), - a history of sars-cov-2 infection in the three months prior to the start of the study, any respiratory distress, - and refusal to sign the informed consent.