Preventing COVID-19: use layers that match the risk
No single measure removes all risk. Ventilation, well-fitted masks, vaccination and staying away from others when ill reinforce each other.
Reduce shared-air risk
Fresh air, effective ventilation and appropriately sized air cleaning can lower risk indoors. Outdoor or well-ventilated settings are generally safer than crowded enclosed spaces when other conditions are similar.
Use masks when risk is higher
A well-fitting mask can be useful in healthcare settings, crowded transport, around people at higher risk or when you are unwell. Fit matters as much as the type of mask.
Vaccination and staying home when ill
Vaccination is important for reducing severe illness. When respiratory symptoms occur, reduce close contact, improve ventilation and use a mask around others when necessary.
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Related guides
Indoor ventilation at home and work: reducing respiratory risk
Better ventilation reduces the build-up of shared indoor air. Practical steps for homes, workplaces, shops and classrooms.
Masks and ventilation: practical layers for reducing respiratory virus risk
Masks and cleaner indoor air are complementary layers that can reduce respiratory-virus risk, especially in crowded or poorly ventilated settings.
How to choose and use a mask: when it still helps
Masks are one layer of risk reduction. Their benefit depends on the setting, fit and the needs of people nearby.
This content is general information, not a diagnosis or individual medical advice. Seek urgent help for severe or rapidly worsening symptoms.