Even before Friday’s landmark study, there has been growing body of evidence that wearing a cloth mask can provide some protection to both the mask wearer and others… and that when folks wear masks it reduces respiratory disease transmission in the community (1,2).

Cloth masks made of household materials provide about 60% filtration of particles of droplet size (range from 3-86%) coming into the wearer (3,4,5).

There is also abundant evidence that masks keep particles inside the mask (source control), which is important due to the high number of people who are infected both without symptoms and before symptoms occur (2).

Mask efficiency improves when multiple layers of fabric are used and when using fabric combinations (6). For example, filtration efficiencies of hybrid materials (such as cotton–silk, cotton–chiffon, cotton–flannel) was >80-90%. Cotton performs better at higher weave densities (i.e., thread count). Gaps caused by improper mask fit can decrease effectiveness, so having a good fit is important.

  1. Howard, J.; Huang, A.; Li, Z.; Tufekci, Z.; Zdimal, V.; van der Westhuizen, H.; von Delft, A.; Price, A.; Fridman, L.; Tang, L.; Tang, V.; Watson, G.L.; Bax, C.E.; Shaikh, R.; Questier, F.; Hernandez, D.; Chu, L.F.; Ramirez, C.M.; Rimoin, A.W. Face Masks Against COVID-19: An Evidence Review. Preprints 2020, 2020040203

  2. C. Raina MacIntyre , Abrar Ahmad ChughtaiView Of The Efficacy Of Face Masks And Respirators Against Coronaviruses And Other Respiratory Transmissible Viruses For The Community, Health- Care Workers And Sick Patients, International Journal of Nursing Studies (2020), doi: https://doi.org/10.1016/j.ijnurstu.2020.103629

  3. A. Davies, et al., Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic? Disaster Medicine Public Heal. Prep. 7, 413–418 (2013).

  4. S Rengasamy, B Eimer, RE Shaffer, Simple Respiratory Protection. Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 201000 nm Size Particles. The Annals Occup. Hyg. 54, 789–798 (2010).

  5. Mvd Sande, P Teunis, R Sabel, Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population. PLOS ONE 3, e2618 (2008).

  6. Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guh. Aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS Nano. 2020;14:6339-6347.

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