Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
Table 1.
Characteristics of the face masks.
| Material | Layers (no) | Thickness (mm) | Mass (g) |
|---|---|---|---|
| Surgical | 3 | 0.4 | 3 |
| Cotton jersey (generic) | 2 | 0.7 | 11 |