Coronavirus: Should I wear a face mask or face shield?

A cashier wearing a mask under a face shield at Sheng Siong supermarket on May 13, 2020.
A cashier wearing a mask under a face shield at Sheng Siong supermarket on May 13, 2020.ST PHOTO: KUA CHEE SIONG

People can choose to wear either a face mask or face shield when they leave the house, according to the Ministry of Health’s guidelines.

For the general public, a face mask or a face shield alone provides adequate protection, doctors say. However, those working in high-risk settings should wear both a mask and shield.

FACE MASK

How to use

• Make sure your nose and mouth are covered.

• There should be no gaps between the mask and your face.

How they work

• Protects your nose and mouth from droplets that may contain virus particles. 

• Prevents the virus from being spread by a sick person by acting as a barrier.

Pros and cons

• Prevents large infectious droplets from landing on a person’s nose and mouth.

• However, airborne aerosols (smaller invisible droplets) can still enter through the gaps.

• There is also a global shortage of surgical masks.

FACE SHIELD

How to use

• Make sure your whole face is covered, from ear to ear and forehead to chin.

• There should be no gaps between the securing headpiece and the plastic shield

How they work

• Protects your eyes and other parts of the face from droplets that may contain virus particles, and prevents the virus from being spread by a sick person by acting as a barrier.

• It also prevents face masks from getting wet. 

Pros and cons

• Relatively easy to make and can be cleaned easily.

• A person’s face is also fully visible, which some people may prefer.

• However, it lacks a good seal around the face, allowing aerosols to penetrate.

When to use

• All types of masks, including face shields and reusable and homemade masks, offer adequate basic protection for the general public, says the Ministry of Health. 

• Plastic spit guards which mainly cover the mouth are not acceptable. 

• Surgical masks should be saved for those who need them most, such as healthcare workers. 

• Healthcare workers are generally advised to use both face shields and face masks, as their work involves long hours of contact with patients and puts them at a higher risk of infection.

VIRAL DROPLETS

Droplets from coughing and sneezing

• A cough: 3,000 droplets.

• A sneeze: 40,000 droplets.

Droplets from talking and breathing

• An infected person with mild or no symptoms talking in a poorly ventilated space for five minutes can generate as many viral droplets as an infectious cough.

• Commuters should avoid talking on trains and buses.

Aerosols (smaller invisible droplets)

• These micron-sized droplets form a cloud that can linger in the air for minutes before they settle on surfaces.

• It is currently unclear whether Covid-19 can be transmitted through aerosols.

Larger visible droplets

• These fall to the floor within about two metres.

Recommended safe distance

 
 

• The US Centres for Disease Control and Prevention recommends safe distancing of two metres based on the assumption that transmission occurs primarily through the larger droplets.

• The World Health Organisation  and Singapore’s Ministry of Health recommend physical distancing of at least one metre.

Travel range of aerosols

• However, it doesn’t mean there are no more droplets beyond two metres.

• Researchers from MIT have observed smaller cough droplets travelling up to five metres and sneeze droplets travelling up to eight metres.

• The travel range of these aerosols suggests that keeping a distance of two metres or more can potentially reduce the possibility of transmission.

Sources: USA Today, New York Times, Ministry of Health, National University Polyclinics, NTUC Health, Parkway Shenton, Alexandra Hospital, Straits Times Graphics