Debates are still ongoing whether face masks can help contain the spread of coronavirus. The World Health Organization does not require everyone to wear face masks as there is not much evidence on how well they work.
But despite this, many countries have made face masks a compulsory on public transport and shops. The UK government's scientific advisory group emergencies (SAGE) argued that with so many people displaying no symptoms at all and yet could be carriers of the virus, masks may prevent unknowingly spreading the virus to others when coughing or sneezing.
If used properly, masks could also prevent people from touching their faces and infecting themselves especially when combined with frequent hand washing and social distancing practices. However, medical-grade masks should be reserved for health workers since they need it the most.
People are now starting to make their own masks at home, but are the masks they have been making effective enough to protect them from the virus? Scientists from the Argonne National Laboratory and the University of Chicago in the United States have studied a variety of materials to make cloth face masks that people can use in the absence of the medical-grade face masks.
'Hybrid' fabrics best to filter aerosol particles
Since many people now are using cloth face masks as an alternative to medical-grade masks, some scientists experimented on a variety of common materials that people can use to make their own face masks.
The team of researchers found that multiple layers and mixed up fabrics worked best to filter coronavirus particles. But if the mask is not the right fit, it can ruin the whole thing. They explained in their new paper that they have carried out their experiment on common fabrics such as cotton, silk, chiffon, flannel, various synthetics, and their combinations.
Overall, they found that a combination of the various fabrics usually used for face masks can provide significant protection against aerosol particles form transmitting.
The research team used an aerosol mixing chamber to sample the number of aerosols in the air. After mixing the aerosol, they then passed the particles through each of the sample fabrics which are secured on the end of the PVC tube and tested the air that went through the material.
They tested the aerosol particles that ranges in sizes, from around 10 nanometers up to 10 micrometers. To put it into perspective, the diameter of a hair's strand measures approximately 50 micrometers in diameter and there are 1,000 nanometer in a micrometer. The coronavirus ranges between 80 to 120 nanometers in diameter.
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The team found little particles. They concluded that 'hybrid' fabrics or also known as layering multiple materials were able to filter most of the aerosol particles. The filtration efficacy of the hybrid fabrics such as the cotton-silk, cotton-chiffon, and cotton-flannel was greater than 80% effective for particles less than 300 nanometers. While more than 90% for particles that are more than 300 nanometers.
"We speculate that the enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration," said the researchers.
Proper using of the mask is important
But mechanical filtration is just the fabric physically catching the particles. The smaller the holes of the fabric, the fewer particles can escape. On the other hand, Electrostatic-based filtration is a little different since it keeps the aerosols inside the static environment.
But none of these matter if you are wearing the mask incorrectly. In the second part of their experiment, they poked small holes in the fabrics and the results imply that gaps caused by an improper fit of the mask can decrease the filtration efficacy of the mask by 60%. This means that whatever the materials used in making the mask, it is important to wear them properly.
The CDC has released guidelines in how to properly wear face masks that you can use for higher efficacy rate. The researchers published their paper in ACS Nano.
