Homemade masks can stop the spread of COVID-19 – but only if they meet certain specifications, a new study finds.
Researchers at the Indian Institute of Science used synthetic cough droplets to model how well different mask types stand up to coronavirus particles.
They found that surgical and N95 masks are still the most effective at stopping coronavirus spread.
Cloth masks may be a suitable alternative if these masks only if they have at least three layers and are made of cotton, the team found.
These findings may be particularly useful for lower-income countries like India, where surgical masks are not easily accessible to the general population.
Cloth masks are effective at stopping coronavirus particles from spreading if they meet certain criteria, a new study suggests (file image)
The researchers tested different cloth options and surgical masks, finding that multi-layer cotton masks worked better than other cloth masks at stopping coronavirus spread
The novel coronavirus primarily spreads through the air, in two possible forms.
Firstly, it can spread through large droplets ejected when an infected person talks, coughs, sneeze, or breathes.
These droplets tend to travel a short distance and drop to the ground.
Secondly, the virus can spread through smaller particles called aerosols.
These particles are also released from an infected person – but they tend to stay in the air for a longer period of time, especially when the space isn’t well-ventilated.
Face masks can block both large droplets and small aerosols.
Studies have shown that surgical masks and N95s work better at blocking coronavirus particles than cloth masks.
As a result, some European leaders and businesses – including several European airlines and the German government – have banned cloth masks in favor of the more-effective surgical masks.
Some American scientists have called for similar regulations in the U.S., along with easier access to surgical masks.
But a new study – published on Tuesday in the journal Physics of Fluids – shows that cloth masks may also be very effective at blocking the coronavirus if they meet certain criteria.
Researchers at the Indian Institute of Science set out to determine which materials and mask formats work best at preventing droplet and aerosol spread.
The scientists used synthetic cough droplets to stimulate the particles released when a person sick with Covid coughs.
When a person with Covid coughs into a mask, their cough droplets spread out along the inside of the fabric – with more effective materials, like cotton and surgical masks (left), reducing spread more than lighter fabrics (right)
They measured the cough droplets’ travel with high-speed imaging, then analyzed these findings to determine how well the droplets might be able to penetrate different types of masks.
While this method doesn’t provide real-world data on cloth masks’ ability to reduce Covid spread in a population, the scientists were able to see exactly what happened when someone coughed into a mask.
The researchers looked at different droplet sizes and speeds, as well as different masks and face coverings commonly used in India.
These face coverings included a handkerchief, a cotton towel, surgical masks, and a summer stole – a type of shawl.
‘Our results show cotton, towel-based fabrics were most effective among the considered fabrics and must be stitched together as multiple layers for making homemade facemasks,’ said study author Saptarshi Basu, a mechanical engineer at the Indian Institute of Science.
‘A three or more-layered homemade mask is recommended, since it can suppress aerosolization significantly.’
This finding aligns with past research, which has shown that the more layers a mask has, the more it’s able to prevent virus spread.
Cough droplets stopped by a mask will spread out along the inside of the mask material, the researchers’ imaging revealed.
Cotton is particularly effective at stopping the cough droplets and reducing spread along the inside of the mask because this fabric has smaller pores – leaving little space for droplets to travel.
Multiple layers of cotton further block the cough droplets from traveling while also stopping large droplets from turning into aerosols, the researchers observed.
The researchers additionally studied the impact of washing a cloth mask, as some scientists have worried that a lot of washing could make a mask less effective.
In this study, however, washing seemed to have a ‘negligible influence’ on the mask’s ability to block coronavirus particles, the researchers said. They saw no impact, going up to 70 wash cycles.
These findings are particularly useful for low- and middle-income countries like India, where surgical masks are not readily available and affordable for everyone.
‘The current study is directed towards those people who cannot use the recommended N95 mask due to lack of convenience, availability, or economic and demographic reasons,’ the researchers wrote.
When N95 and surgical masks aren’t available, multi-layer cotton is the best option.
Still, the researchers write that any mask is better than nothing: ‘one should always wear whatever makeshift mask is available.’
The researchers also note that multi-layer cotton masks may be useful for agricultural workers and medical settings outside of Covid.
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