Not all masks are created equal.

By Mariusz Bogacki, Researcher and Science Communicator, Edinburgh

Researchers at the Mel and Enid Zuckerman College of Public Health in Arizona, USA, tested a variety of mask materials and their effectiveness in stopping the spread of airborne viruses such as Covid-19. The study analysed how wearing different masks compared to wearing no mask at all, and estimated the risk of infection for short (30 seconds) and long (20 minutes) inhalation exposure in a highly contaminated environment.

The masks used in the experiment included the N95 and N99 respirator masks, surgical masks and non-traditional material masks (silk, tea towel, vacuum cleaner bag, cotton mix, 100% cotton shirt, tea towel, pillowcase, silk, linen and scarf).

Unsurprisingly, the N99 and N95 respirator masks, respectively, were the most successful at reducing the risk of contamination. However, the researchers pointed out that due to the ongoing shortages in their production, these masks should always be reserved for front-line healthcare staff.

Out of non-traditional materials it was the vacuum cleaner bag that managed to protect from spreading and inhaling the airborne contaminated particles best. This is due to the bag’s filter, which can be re-purposed and inserted into filter pockets of any cloth masks. Probably a better idea than walking around wearing a vacuum cleaner bag on your face! While scarf offered the lowest protection, other tested materials performed similarly in terms of reducing the risk of contamination. It appears that the denser the fibre of a material, the better it is at filtering.

The researchers found that the time spent in a contaminated environment was a crucial factor in infection rate. The longer a person spends in an environment where a virus is present, the less effective a mask becomes. Other conditions impacting the risk of infection were the number of people and distance between them.

The experiment also confirmed the fact that no mask can completely filter out all infectious particles. However, perhaps the most important overall finding is that wearing a mask definitely works in reducing the risk of inhalation and spread of virus contaminated clouds of particles. The less virus is put out into the air, the less contaminated the environment becomes. It is indeed worth remembering that wearing a mask is not only about protecting yourself but about minimising the spread of the virus to other people - and therefore protecting other, potentially more vulnerable people.