The Ministry of Health recommends wearing medical masks properly to prevent coronavirus

A 2013 study found that large droplets of saliva range in size from about 75 to 360 micrometers (1 micrometer = 1000 nanometers). Therefore, they can be easily captured by regular medical masks that effectively filter particles larger than 5 micrometers.

Using a medical mask properly will prevent large droplets containing the virus from being expelled from a sick person through sneezing or coughing.

Regular non-woven medical masks have 3 layers with different uses.

The outer layer has waterproof properties, effectively preventing liquid particles from splashing out when a sick person sneezes, coughs, breathes heavily, etc. The outer surface is usually light blue for easy identification. The correct way to wear a mask is to leave the colored layer facing out.

Face masks have become an "inseparable" item these days for people in China - the epicenter of the acute respiratory infection caused by nCoV.

The middle layer has the function of preventing splashing of liquid particles and must filter dust and bacteria. This is the layer that determines the quality of the mask. A "standard" filter layer must allow air to pass through easily, creating ventilation for the user, but must have a structure sufficient to filter extremely small dust particles and bacteria.

According to the FDA (USA), one of the criteria for evaluating the quality of masks is "Bacterial Filtration Efficiency" (BFE).

Masks are only classified as "medical masks" when they have a BFE > 95%. Choosing a good mask means choosing the one with the highest BFE. A mask with a BFE > 99% is the best choice.

So how to use a medical mask properly? Here are the recommendations of the World Health Organization:

- Use the mask only once and then throw it in a safe, covered trash can.

- When wearing a mask, the blue side must be facing out because this side is waterproof, large droplets of saliva will not penetrate inside and may fall down. The white side is hygroscopic so it should be facing inward, allowing the exhaled breath to penetrate the mask.

- Masks must cover both nose and mouth.

A standard medical mask must meet all criteria.

- When removing the mask, only hold the ear straps, remove and put in a safe trash can. Absolutely do not use your hands to hold the mask to remove it. The habit of crumpling the mask with your hands will cause viruses and other pathogens to be transmitted to your hands.