About medical face mask

1. What is medical mask (aka surgical mask or face mask)?

Definition by FDA (The Food and Drug Administration) is:
A surgical mask is a loose-fitting, disposable device that creates a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment.

Structure of a typical medical mask

2. When and how to use masks

World Health Organization (WHO) gives suggestions:
If you are healthy, you only need to wear a mask if you are taking care of a person with suspected 2019-nCoV infection.
Wear a mask if you are coughing or sneezing.
Masks are effective only when used in combination with frequent hand-cleaning with alcohol-based hand rub or soap and water.
If you wear a mask, then you must know how to use it and dispose of it properly.

3. How to protect yourself from Coronavirus Disease 2019 (COVID-19)?

Centers for Disease Control and Prevention (CDC) gives suggestions:
wear a facemask if you are sick
If you are sick: You should wear a facemask when you are around other people (e.g., sharing a room or vehicle) and before you enter a healthcare provider’s office. If you are not able to wear a facemask (for example, because it causes trouble breathing), then you should do your best to cover your coughs and sneezes, and people who are caring for you should wear a facemask if they enter your room. Learn what to do if you are sick.

If you are NOT sick: You do not need to wear a facemask unless you are caring for someone who is sick (and they are not able to wear a facemask). Facemasks may be in short supply and they should be saved for caregivers