Homemade masks could stop the spread of COVID-19 if they meet certain specifications, a new study finds.
Researchers at the Indian Institute of Science used synthetic cough drops to model how well different mask types resist coronavirus particles.
While surgical and N95 masks are still the most effective at stopping the spread of the coronavirus, cloth masks may be a suitable alternative if these masks have at least three layers and are made of cotton, the team found.
These findings may be particularly helpful for lower-income countries such as India, where surgical masks are not readily accessible to the general population.
Cloth masks are effective at stopping the spread of coronavirus particles if they meet certain criteria, new study suggests (file image)
The researchers tested different fabric options and surgical masks, and found that multilayer cotton masks worked better than other fabric masks in stopping the spread of the coronavirus.
The new coronavirus spreads mainly through the air, in two possible forms.
First, it can spread through large droplets emitted when an infected person talks, coughs, sneezes, or breathes.
These drops tend to travel a short distance and fall to the ground.
Second, the virus can spread through smaller particles called aerosols.
These particles are also released by an infected person – but they tend to remain airborne for extended periods of time, especially when the room is not properly 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.
Some US scientists have called for similar regulations in the US, along with easier access to surgical masks.
But a new study – published Tuesday in the journal Physics of Fluids – shows that cloth masks can also be very effective in blocking the coronavirus if they meet certain criteria.
Researchers at the Indian Institute of Science wanted to determine which materials and mask sizes work best to prevent the dispersion of droplets and aerosols.
The scientists used synthetic cough drops to boost the particles released when a person who is sick with Covid coughs.
When a person with Covid coughs in a mask, their cough drops spread along the inside of the fabric — with more effective materials, such as cotton and surgical masks (left), reducing the spread more than lighter fabrics (right)
They measured the travel of the cough droplets with high-speed imaging and then analyzed these findings to determine how well the droplets would be able to penetrate different types of masks.
While this method doesn’t provide real data on cloth masks’ ability to reduce the spread of Covid 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 velocities, as well as different masks and face coverings commonly used in India.
These face coverings include a handkerchief, a cotton towel, surgical masks and a summer stole – a type of scarf.
“Our results show that cotton towel-based fabrics were the most effective among the fabrics considered and should be sewn together as multiple layers for making homemade face masks,” said study author Saptarshi Basu, a mechanical engineer at the Indian Institute of Science.
“A homemade mask with three or more layers is recommended, as it can significantly suppress the spray.”
This finding is consistent with previous research, which has shown that the more layers a mask has, the more it can prevent virus spread.
Cough drops blocked by a mask spread along the inside of the mask material, the researchers’ imaging showed.
Cotton is particularly effective at stopping the cough drops and reducing their spread along the inside of the mask, as this fabric has smaller pores – leaving little room for the droplets to travel.
Multiple layers of cotton further prevent the cough drops from traveling, while also preventing large droplets from turning into aerosols, the researchers noted.
The researchers also studied the impact of washing a cloth mask, as some scientists feared that too much washing could make a mask less effective.
However, in this study, washing appeared to have a “negligible impact” on the mask’s ability to block coronavirus particles, the researchers said. They saw no impact, up to 70 washes.
These findings are particularly helpful for low- and middle-income countries such as India, where surgical masks are not readily available and affordable for everyone.
“The current study is aimed at 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 are not available, multilayer cotton is the best option.
Still, the researchers write that any mask is better than nothing: “One should always wear the makeshift mask that is available.”
The researchers also note that multilayer cotton masks could be useful for farm workers and medical facilities outside of Covid.