Excite

COVID-19 masks: the best materials to use if making your own

COVID-19 has made the world a scary place. The shops you used to breeze into without a care in the world are now places you queue up to enter. You've been shut out of your workplace and had restrictions imposed on how often you can leave the house. Thankfully, things are getting better. We always knew they would with time. That's because the majority of us have been following government guidelines to keep two metres apart, and some of us have taken the added measure of wearing a mask. As with all the other essential items, you might be having trouble finding a suitable mask. If you've tried to make one for yourself, listen to the experts who have decided which materials are best to stop the spread of SARS-CoV-2.

Testing phase

Boffins at the Argonne National Laboratory and the University of Chicago have been testing common materials for many weeks now to find the one with the best mechanical and electrostatic filtration properties. During their research, the team found that multiple layers of mixed fabric worked best to filter particles. In their paper, which you'll find at acs.org, the researchers reveal they "…carried out these studies for several common fabrics including cotton, silk, chiffon, flannel, various synthetics, and their combinations." They conclude that "Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles."

The experiment

To begin with, the team used an aerosol mixing chamber to sample the number and types of aerosol in the air. They then passed each particle through each test fabric, which were secured on the end of a PVC tube. They then sampled the air that made it through the material. The range of particles they tested was vast – from 10 nanometres up to 10 micrometres. Those numbers might not mean anything to you, so let's put that in perspective. A human hair is around 50 micrometres in diameter, which is five times wider than the largest particle measurement they tested for.

Particles

There's some debate as to whether tiny particles, such as the ones they were testing for, can spread COVID-19. That tells you how thorough these scientists were. They found that a hybrid fabric made from layers of different materials was the best at blocking particles. In their paper, the researchers write, "Filtration efficiencies of the hybrids (such as cotton–silk, cotton–chiffon, cotton–flannel) was >80 per cent (for particles <300 nanometres) and >90 per cent (for particles >300 nanometres)." They speculate that a combination of "mechanical and electrostatic-based filtration" is the reason for the performance of the hybrid.

Mechanical filtration

Mechanical filtration refers to the material physically ability to catch particles. The high-tread count in cotton meant it worked best. It's a simple equation – the smaller the holes in the fabric, the fewer particles are able to escape.

Electrostatic-based filtration

This is a little different, but anyone who's heard of static electricity will be able to grasp the basics. A material like polyester produces a lot of static, and it can easily be transferred to another person. The scientists were looking for the opposite – a material that retained the aerosols within the static environment.

Fitting

The only issue let to look at is fitting the mask. If it's not fitted correctly, it's far less effective. "Our studies also imply that gaps (as caused by an improper fit of the mask) can result in over a 60 per cent decrease in the filtration efficiency."

United Kingdom - Excite Network Copyright ©1995 - 2020