Masks are only effective only when used in combination with frequent hand-cleaning and hand disinfection. Start by cleaning your hands with alcohol-based hand rub or soap and water. Avoid touching the mask while using it. Replace the mask with a new one as soon as it gets damp. Single-use masks should not be reused. Remove the mask: from behind (do not touch the front of mask); discard immediately in a closed bin; clean hands with alcohol-based hand rub or soap and water (source: WHO)
That’s the answer.
Corona virus ranges from between 0.06 and 0.14 microns in size. Still Respirator filters (which are designed to filter particles with a size of 0.3microns) are effective to prevent viral infection from the SARS-CoV-2 virus due to a physical phenomena which is called the brownian motion. It is recommended to use Respirators > N95 (American standard) or at least FFP 2 (European standard)