First of all, it is important to know that the visor is a mode of protection that is never worn alone.
This device is only used to deflect the droplets emitted by a person who is at risk of coughing, sneezing or spitting during manoeuvres such as, for example, a PCR test or a session of physiotherapy breathing etc. One of the visor's purposes is to protect the eyes (which the mask does not do), as coronaviruses can also enter via this channel. However, this remains a rare mode of contamination.
The visor is not waterproof. Inhalation causes a flow of air to pass through the sides of the visor, which will take the opposite route on exhalation, so there is no protection against Covid 19.
This device does not absorb anything: as soon as the visor has been soiled, its surface must be washed according to a standardised procedure, with a virucidal solution. The decontamination of the different parts of a visor is more complicated than that of a fabric mask. They cannot be sterilised in conventional hospital autoclave facilities at 100°C.
Finally, a visor does not filter anything: it is therefore worn IN ADDITION TO THE MASK, which remains essential to stop small particles (and therefore viruses) as the air breathed in or out passes through the thickness of its mesh.
Wearing a visor on its own makes no sense outside of trades where you have to protect your face from direct (=straight line) projections of relatively large particles.
Source : Le Louvain Médical (Revue de la Faculté de Médecine et Médecine Dentaire de l’Université Catholique de Louvain)
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