Mask use in the context of COVID-19: interim guidance, 1 December 2020

This document, which is an update of the guidance published on 5 June 2020, includes new scientific evidence relevant to the use of masks for reducing the spread of SARS-CoV-2, the virus  that causes COVID-19, and practical considerations. It contains updated evidence and guidance on the following:
• mask management;
• SARS-CoV-2 transmission;
• masking in health facilities in areas with community, cluster and sporadic transmission;
• mask use by the public in areas with community and cluster transmission;
• alternatives to non-medical masks for the public;
• exhalation valves on respirators and non-medical masks;
• mask use during vigorous intensity physical activity;
• essential parameters to be considered when manufacturing non-medical masks (Annex).

Mask use in the context of COVID-19: interim guidance, 1 December 2020 (who.int)