This information is sourced from the Department for Transport, the British Lung Foundation (BLF), The Cabinet Office and Keep Safe:

The Cabinet office advise that:

You do not need to wear a face covering if you have a legitimate reason not to. This includes (but is not limited to):

• young children under the age of 11 (PHE do not recommended face coverings for children under the age of 3 for health and safety reasons)
• not being able to put on, wear or remove a face covering because of a physical or mental illness or impairment, or disability
• if putting on, wearing or removing a face covering will cause you severe distress
• if you are travelling with or providing assistance to someone who relies on lip reading to communicate

Exemption cards:

GOV UK have published face covering exemption cards and badges

The Department for Transport have produced a Face coverings exemptions list

The BLF advise people with lung conditions to try and get used to a face covering for short periods of time at home. But that if they feel too breathless they do not have to wear one. They have produced a downloadable graphic and a list of exemption cards for different bus and train companies

Keep Safe has produced an exemption card to help people with a learning disability explain why they are not wearing a mask