Where, and what masks to use? If you have to, how to reuse them?

"Coronaviruses can be present in the environment in two-particle size: the viruses themselves are 60-120 nanometers (nm) in size, but in this form, this type of virus is found in the presence of a large number of patients. The virus is usually attached to saliva droplets ranging from 10 to 1000 micrometres in size.

In any case, the most effective means of retaining particles in the 100 nm range are FFP2-3 class respirators (commonly referred to as N95 or 99 in the US market).

The surgical mask holds only 14-19% of small (100 nm range) virus particles, and the efficiency of homemade masks is less than 10 percent. Similar results were obtained by the researchers of the Lithuanian Energy Institute who carried out filtration efficiency studies. Therefore, at least FFP2 respirators (in other words, N95), even sterilized several times, should be provided to medical personnel and other persons who care for the patient at short distances, but should be properly secured.

Studies have shown that ethylene oxide steam sterilization does not significantly reduce the filtration properties of the respirator tissue. It is described in other countries, that the same applies to heat sterilization (30 min at 60 ° C) or UV irradiation. However, it is noticeable that sterilization may affect important properties other than the filter tissue, in particular adherence to the face, nasal compression, and straining rubber bands. The fact that a sterilized FFP2 respirator lets through more particles than FFP1 indicates that a good fit on the face is an essential condition for the respirator's effectiveness.

Most studies and recommendations indicate that this virus is most effective in the transmission through the saliva droplets 10 to 1000 micrometres in size. Surgical masks and homemade masks are effective in retaining these droplets (relatively large particles) so they can protect against the direct effects of sneezing.

Homemade masks could be thermally sterilized by maintaining them for half an hour at 60 ° C, for example in an oven. "

Under ideal conditions, these masks should be disposable. However, no state has been able to accumulate enough of them to cover this pandemic, so we can rarely work under ideal conditions now.