[3] Prior to the COVID-19 pandemic, reusable cloth face masks were predominantly used by healthcare workers in developing countries and were especially prominent in Asia.

In addition, respirators, unlike cloth face masks, are regulated for their effectiveness based upon efficiency of minimum particle size filtered and/or maximum penetrating particle (MPP) size, along with other criteria such as outer splash/spray protection, inner splash/spray absorption, contaminant accumulation and shedding, air flow, and inflammability.

[2] They are also used by the general public in household and community settings as perceived protection against both infectious diseases and particulate air pollution and to contain the wearer's exhaled virus laden droplets.

[8] The World Health Organization (WHO) recommends that cloth face masks should be worn in public where social distancing is not possible to help stop the spread of coronavirus.

[24] It is important to note that mask wearers are more likely to engage in other hygiene measures such as hand washing and social distancing.

Best practice is to implement multiple prevention techniques to reduce risk, as characterized by the Swiss cheese model.

[27] An experiment carried out in 2013 by Public Health England, that country's health-protection agency, found that a commercially made surgical mask filtered 90% of virus particles from the air coughed out by participants, a vacuum cleaner bag filtered out 86%, a tea towel blocked 72% and a cotton t-shirt 51%—though fitting any DIY mask properly and ensuring a good seal around the mouth and nose is crucial.

[29][30][31][32] Filter efficiency can be improved with multiple layers, high weave density, and a mix of different types of fabrics.

Cotton is the most commonly used material, and filter efficiencies can reach >80% for particles <300 nm with fabric combinations such as cotton-silk, cotton-chiffon, or cotton-flannel.

[33] In Roman times, Pliny the Elder recommended that miners use animal bladders to protect against inhaling lead oxides.

Some followers of Jainism, which originated in India around 500 B.C.E, wear cloth masks to avoid accidentally inhaling insects as part of practicing ahimsa.

[38] In the early modern period, the plague-doctor costume included a beaked face-mask worn to protect the wearer from infectious "miasma".

Conventional cowboy attire in the American West often included a bandanna, which could protect the face from blown dust and also potentially doubled as a means of obscuring identity.

[40][41] Cloth face masks were promoted by Wu Lien-teh in the 1910–11 Manchurian pneumonic plague outbreak, although Western medics doubted their efficacy in preventing the spread of disease.