The use of masks is part of a comprehensive package of the prevention and control measures that can limit the spread of certain respiratory viral diseases, including COVID-19. Masks can be used either for protection of healthy persons (worn to protect oneself when in contact with an infected individual) or for source control (worn by an infected individual to prevent onward transmission).
However, the use of a mask alone is insufficient to provide an adequate level of protection or source control, and other personal and community level measures should also be adopted to suppress transmission of respiratory viruses. Whether or not masks are used, compliance with hand hygiene, physical distancing and other infection prevention and control (IPC) measures are critical to prevent human-to-human transmission of COVID-19.
Types of mask to consider
Medical masks should be certified according to international or national standards to ensure they offer predictable product performance when used by health workers, according to the risk and type of procedure performed in a health care setting. Designed for single use, a medical mask’s initial filtration (at least 95% droplet filtration), breathability and, if required, fluid resistance are attributed to the type (e.g. spunbond or meltblown) and layers of manufactured non-woven materials (e.g. polypropylene, polyethylene or cellulose). Medical masks are rectangular in shape and comprise three or four layers. Each layer consists of fine to very fine fibres. These masks are tested for their ability to block droplets (3 micrometres in size; EN 14683 and ASTM F2100 standards) and particles (0.1 micrometre in size; ASTM F2100 standard only). The masks must block droplets and particles while at the same time they must also be breathable by allowing air to pass. Medical masks are regulated medical devices and categorized as PPE.
The use of medical masks in the community may divert this critical resource from the health workers and others who need them the most. In settings where medical masks are in short supply, medical masks should be reserved for health workers and at-risk individuals when indicated.
Non-medical (also referred to as “fabric” in this document) masks are made from a variety of woven and non-woven fabrics, such as polypropylene. Non-medical masks may be made of different combinations of fabrics, layering sequences and available in diverse shapes. Few of these combinations have been systematically evaluated and there is no single design, choice of material, layering or shape among the non-medical masks that are available. The unlimited combination of fabrics and materials results in variable filtration and breathability.