Specifications to make cloth masks as alternative protection against viral particles
Sunday Omeike PhD
Saturday, 2 May 2020
The novel coronavirus disease continues its global rampage with over three million cases, leading to shortage of PPE materials available to frontline health workers, especially facemasks.
This prompted the World Health Organization’s advice against public use because it offers little or no protection against the virus. However, recent evidences have shown otherwise. SARS-CoV-2 virus survives in air for long periods but its links to infection remains inconclusive. Regardless, countries have mandated facemasks in public as lockdowns gradually ease and Nigeria is no exception, with states approving alternative locally made cloth masks due to conventional facemask shortage.
Researchers at Netherland’s National Institute for Public Health and the Environment1, and Public Health England (PHE)2 envisaged this future occurrence a decade ago and stated cloth masks could offer three-fold less protection, though such level of protection could prove vital, especially if facemask shortage is experienced during pandemic and epidemics.
Cloth masks have gained social popularity and conspicuously completes the attire of Prof. Ben Ayade, Cross River state governor. Babajide Sanwo-Olu has also donned it and his Lagos State government plans to distribute three million cloth masks “made to specification” to the vulnerable. The country’s agency for food and drugs control, NAFDAC recently advised on its proper use, but how well does it screen viral particles and of what material should it be made in order to reduce the risk of COVID-19.
“Any type of general mask use is likely to decrease viral exposure and infection risk on a population level,” the Netherland report concluded, while PHE advised “homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection.”
In response to the present outbreak, a research team in USA’s Argonne National Laboratory3 further determined type and fabric arrangement for improved protection against viruses. Particle size of concern was 0.3 – 6 µm which the SARS-CoV-2 virus falls within, and they found that cotton, natural silk and chiffon provides over 50% protection if viral particles are present in aerosols which are basically dispersed via mouth and nose activity. However, these must be tightly weaved, meaning we have a duty to educate and provide specific details to tailors and seamstresses in shops and factories contracted to make fabrics into facemasks.
Tightly weaved layers of cotton, the most widely used material for cloth masks, could provide 80% depending on particle size. Cotton desirability is not restricted to availability but also for reduced porosity, an important property necessary to screen out virus-transporting aerosols. However, cotton quilt, which has a fibrous middle material acting as batting, provides best protection- 96%- because the “fibrous nature of the batting aids in the superior performance at small particle sizes.”
Combinations of cotton with other types of fabric such as two layers of natural silk, two layers of chiffon, using cotton−polyester as batting between two layers of cotton in cloth mask would screen 8 in 10 viral particles (80% efficiency). Cloth mask produced using four layers of silk also provides good protection against particulates in the virus range.
Finishing is an important part of fashion designers to sew to style and fit, and it is also a critical element in making cloth masks because it could make or mar effectiveness. Edges and contours should fit to size of user’s face, failure to ensure which results in over 50% reduction in filter efficiency, possible contaminated air proliferation, and increased probability of inhaling viral particles.
Therefore, as cases continue to rise, community spreading in full swing and government eases lockdown from May 4, Nigerians should not settle for any mask but commission a sleuth of masks made to the right specification. Its screening efficiency could prove crucial to protection against the viral particles causing COVID-19 during outdoor activities.
Sunday Omeike, PhD is a Microbiology Lecturer, science communicator and ASLN Fellow. He tweets @OmeikeSunday
1. van der Sande M., P. Teunis, R. Sabel, 2008. Professional and home-made face masks reduce exposure to respiratory infections among the general population. PLoS ONE, DOI: 10.1371/journal.pone.0002618
2. Davies A., K-A. Thompson, K. Giri, G. Kafatos, J. Walker, A. Bennett, 2013. Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Disaster Medicine and Public Health Preparedness. DOI: 10.1017/dmp.2013.43
3. Konda A., A. Prakash, G.A. Moss, M. Schmoldt, G.D. Grant, S. Guha, 2020. Aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS Nano, DOI: 10.1021/acsnano.0c03252.