Several supermarkets across the UK have said they will make face coverings compulsory.
Tesco, Asda and Waitrose are the latest chains to say they will deny entry to shoppers who do not wear face masks unless they are exempt.
It follows a similar move by Morrisons, while Sainsbury's says it will also challenge those who flout the rules.
So what protection do masks offer, and what sort can be worn?
Why should we wear a face covering?
Face coverings reduce the spread of coronavirus droplets from coughs, sneezes and speaking.
They should mainly be worn to protect other people from coronavirus, rather than yourself.
When worn correctly, they should cover the nose and mouth, which are the main confirmed sources of transmission.
They can help to reduce the spread of the virus from people who are contagious, including those who have no symptoms, or are yet to develop them.
There is also evidence they can offer some protection to the wearer, although they are not a replacement for social distancing and hand-washing.
Where must they be worn in the UK?
Face coverings are now compulsory across the UK when:
- Travelling on public transport
- In shops, supermarkets and shopping centres
- Not seated at a table to eat or drink in hospitality venues (when open according to the tier system and outside of lockdown)
People can be refused travel for not following the rules or fined as a last resort. In England and Northern Ireland the police can issue a £200 fine to someone breaking the face covering rules. In Scotland and Wales, a £60 fine can be imposed. Repeat offenders face bigger fines.
- Banks, building societies and post offices
- Places of worship
- Museums, galleries and entertainment venues
- Libraries and public reading rooms
Scotland also requires face coverings to be worn in indoor spaces, such as staff canteens and corridors in workplaces. It no longer requires couples to wear them when exchanging marriage vows.
In Wales, face coverings must be worn in all indoor public places by customers and staff.
In Northern Ireland, they must be worn in "any other indoor place where goods or services are available to buy or rent".
Does everyone have to wear one?
Some people do not have to wear a face covering. They include:
- Children (under 11 in England or Wales, under 13 in Northern Ireland, under five in Scotland)
- Those unable to put on or wear a face covering because of a physical or mental illness or disability
- People for whom wearing or removing a face covering will cause severe distress
- Anyone assisting someone who relies on lip reading to communicate
You can remove your mask if:
- You need to eat, drink, or take medication
- A police officer or other official asks you to, or for shop staff to verify your age
- You are entering a shop to avoid harm, if you do not have a mask on you
Young children should not wear face masks because of the risk of choking and suffocation.
Do you have to prove if you are exempt?
If you have an age, health or disability reason for not wearing a face covering, government guidance makes it clear that you do not have to show any written evidence for why you are exempt.
You do not need to seek medical advice or request a letter from a medical professional about your situation, and the government does not provide exemption cards or badges.
However, the government has provided some suggested templates which people can use if they wish.
What are the face-covering rules in schools?
Primary and secondary schools in the UK have moved to remote learning for most pupils, except for children of critical workers and those deemed vulnerable, who can still physically go to school each day.
The government does not recommend wearing face coverings in schools and colleges because of the Covid controls already in place.
However, each nation is adopting different rules:
- In England, secondary schools have the ''discretion'' to require face coverings in communal areas, where social distancing is not possible, but can be mandatory if local restrictions require them
- The Scottish government says all secondary school pupils should wear face coverings in corridors and communal areas, and senior pupils (years S4-S6) and their teachers must wear them in class
- In addition, all staff in Scottish schools must wear masks where social distancing is not possible
- In Wales, face coverings are recommended in high schools when social distancing is "unlikely to be maintained", but are not compulsory
- In Northern Ireland, face coverings must be worn in the corridors of post-primary schools
Can I make one myself?
The BBC has created a guide on how to make your own face covering.
The government has issued its own advice too.
Do face coverings work?
Face coverings do not give the wearer as much protection as the masks that healthcare workers wear.
World Health Organization (WHO) advice says non-medical face coverings should be worn in public where social distancing is not possible.
They help us protect each other and reduce the spread from people who are contagious but have no symptoms, or are yet to develop symptoms.