Masks have become mandatory in closed places and, in many countries, even outdoors. Some masks, such as surgical ones, must be discarded after their use, other masks, such as those FFP2 (N95) or cloth face masks, DIY or purchased in the chemist’s shop, are instead reused but, to do this, they have to be sanitized after each use. Let's see why the masks have to be sanitized after their use and how this can be done.
Coronavirus, why masks need to be sanitized
The masks help us protect ourselves and others, combined with other measures such as social distancing and hand hygiene with soap and water and disinfectant solutions that contain at least 60% alcohol. Precisely for this function, however, infected material can settle on the mask. Studies have observed that the novel coronavirus resists outside the body on surfaces and that, on the external surfaces of the masks, it can live up to 7 days (Chin et al, The Lancet, 2020). When we remove the mask, therefore, we should be very careful to remove it without the external surface coming into contact with the face and, immediately after, we have to wash the hands thoroughly. Then we need to sanitize the mask, let's see how. The following indications are the result of the work of scientists and have been published in international journals.
Coronavirus, how to sanitize masks
There are several ways to destroy the virus but it is also important to preserve the filtering power of the mask. In fact, the masks are designed to oppose the passage of the virus with a mechanical barrier, namely the path for larger particles becomes too tortuous to be able to continue, and with an electrostatic barrier, able to attract and retain even the smallest particles. Alcohol and bleach destroy the electrostatic charge of the mask that, as we have seen, is vital for its function. The scientists observed that after only one treatment with alcohol the filtering power of the mask had dropped from 96% to 56% while with bleach up to 73% (Liao et al, ACS Nano, 2020). For those who need to sanitize the mask at home and do not have instruments available in the hospital, it is advisable to subject the mask to heat in this way. The mask is immersed in hot water at a temperature above 56° C, generally between 60 and 80° C, for 30 minutes. Then, to restore the electrostatic barrier, the mask is dried with a non-static hair dryer for 10 minutes. To test the electrostatic barrier, just bring pieces of paper close to the mask and check if they are attracted (Mackanzie et al, Engineering, 2020). This method is good for FFP2 (N95) type masks but not for cloth face ones. In this case, the advice is to wash them in the washing machine following the manufacturer's instructions. In any case, whether it is cloth face masks or FFP2, it is possible to reuse them only for a limited number of times. Generally, 50 hygiene treatments are indicated in the packaging recommendations, then the mask should be changed.
