Face Masks

By Janet von Konsky Miller, MPH


As the week-3 SIP closes amidst changing guidelines for wearing face masks during essential outings, it was delightful to see my SIP-mate dive into the art and craft of face mask making yesterday. He experimented with scarfs and shop towels.

While he was busy creating, I dove into learning more about the science behind effective face masks. Here is what I found:

N95 masks are 95% effective as a barrier against particles that are 0.3 microns in size.1, 2  This compares to surgical masks which are effective only up to 65%.3  Whereas the surgical masks are a loosely worn barrier, the NIOSH certified N95 masks fit snugly against the face.1 As we reserve the N95 and surgical masks for the health care work force, we must turn to creatively repurposing home items for home-made face masks.

For the home-made face mask, different fabrics offer different amounts of protection. While T-shirt type fabric may be too thin to be very helpful, two layers of tightly woven fabric offers pretty good protection, according to a North Carolina anesthesiologist who tested different fabrics for effectiveness. The report suggests that if you don’t have fabric with a 180-thread count, use a less tightly woven fabric along with a flannel layer.3

A Los Angeles based clothing manufacturer (Suay Sew Shop) experimented with fabric masks lined with shop towels. This organization tested masks against 0.3 micron sized particles and found that cotton masks were up to 60% effective at blocking particles, and cotton masks lined with shop towels were 93% effective.4, 5 

When studying the effectiveness of 2-layer cotton face masks compared to medical masks in a healthcare setting, researchers found that cloth masks were less effective than the medical masks in preventing rhinovirus infection when worn continuously. Though there were challenges with the control group in the study design, the researchers hypothesized that moisture content and tightness of weave may be factors influencing the effectiveness of cloth masks.6

It is important to remember that the face mask recommendation does not diminish the importance of social distancing during this pandemic, but may be helpful in reducing transmission when participating in essential outside activity. 

It is also important to understand how to properly use the face masks:7

  • Wash hands before putting on a face mask
  • Make sure both the nose and mouth are covered (I saw someone yesterday who just covered the mouth!)
  • Don’t touch the mask
  • If it is wet, replace it
  • Remove a mask from the straps, not the body of the mask
  • Wash hands after removing the mask

Home-made fabric masks may be laundered after use, but adding harsh chemicals to the wash is not recommended.3

Guidelines are updated as more is learned about the SARS Cov 2 virus that causes COVID-19. The virus is currently believed to be airborne which means it can remain in the air even if the infected person is not close by.8 It can take up to 2 weeks for symptoms to appear after exposure.9  Not only are asymptomatic infected people contagious, those who have had the virus may continue to be contagious from 8 days to 37 days after recovery.10, 11  Wearing a face mask may reduce viral transmission when worn by infected individuals.12 Due to asymptomatic transmissions, wearing a face mask during essential activity away from home may help stop the spread of the virus.

So much has changed in the last month for everyone, and while it may be difficult to embrace ever-changing guidelines, it can be an opportunity for some creative SIP mask-making activity!


1FDA. (2020). N95 Respirators and Surgical Masks (Face Masks). Retrieved from https://www.fda.gov/medical-devices/personal-protective-equipment-infection-control/n95-respirators-and-surgical-masks-face-masks

2CDC. (2009). N95 Respirators and Surgical Masks. Retrieved from https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/

3NBC News. (2020). Making your own face mask? Some fabrics work better than others, study finds. Retrieved from https://www.nbcnews.com/health/health-news/making-your-own-face-mask-some-fabrics-work-better-others-n1175966

4Business Insider. (n.d.). Using blue shop towels in homemade face masks can filter particles 2x to 3x better than cotton, 3 clothing designers discover after testing dozens of fabrics. Retrieved from https://www.businessinsider.com/homemade-mask-using-hydro-knit-shop-towel-filters-better-2020-4

5Daily Mail. (2020). Designers find that layering two blue shop towels inside cotton face masks makes the most effective homemade PPEs. Retrieved from https://www.dailymail.co.uk/news/article-8187603/Designers-say-layers-blue-shop-towels-inside-cotton-masks-help-effectiveness-homemade-PPEs.html

6 MacIntyre, C.R., Seale, H., Dung, T.C., Hien, N.T., Nga, P.T., Chughtai, A.A., Rahman, B., Dwyer, D.E., & Wang, Q. (2015). A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJOpen. 5:e006577. doi:10.1136/bmjopen-2014-006577

7WHO. (n.d.) Coronavirus disease (COVID-19) advice for the public: When and how to use masks. Retrieved from https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/when-and-how-to-use-masks

8Johns Hopkins Medicine. (n.d.). Coronavirus Disease 2019 vs. the Flu. Retrieved from https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/coronavirus-disease-2019-vs-the-flu

9Yale Medicine. (2020). 5 Things Everyone Should Know About the Coronavirus Outbreak. Retrieved from https://www.yalemedicine.org/stories/2019-novel-coronavirus/

10Chang et al. (2020). Time Kinetics of Viral Clearance and Resolution of Symptoms in Novel Coronavirus Infection. American Thoracic Society. March 23: 1-12. doi: 10.1164/rccm.202003-0524LE. https://www.atsjournals.org/doi/pdf/10.1164/rccm.202003-0524LE

11Zhou, et al. (2020). Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. The Lancet. 395( 10229):P1054-1062. doi: https://doi.org/10.1016/S0140-6736(20)30566-3

12Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C., Chan, K.H., McDevitt, J.J., Hau, B.J.P., Yen, H.L., Li, Y., Ip, D.K.M., Peiris, J.S.M., Seto, W.H., Leung, G.M., Milton, D.K., & Cowling, B.J. (2020). Respiratory virus  shedding in exhaled breath and efficacy of face masks. Nature Medicine. 26: 676–680. doi.org/10.1038/s41591-020-0843-2

Last Updated 5/21/20