Reusable cloth masks after being washed and dried remain effective for a year in filtering out airborne particles, including the viral ones, as per a new study conducted in the United States. The study was conducted at the University of Colorado Boulder and was published in the journal Aerosol and Air Quality Research. It also confirmed the previous research that layering a cotton mask on top of a surgical mask, given that it perfectly fits on the face, provides more protection than the cloth ones.
How Was The Research Conducted?
For this study, the scientists didn’t test the mask on real people. Instead, they used the following mechanism:
- Several double-layered squares of cotton were created.
- They were repeatedly washed and dried 52 times, which is the number of weekly washes in a year.
- The cotton squared were tested between about every 7 cleaning cycles.
- For testing, cotton was mounted on one end of a steel funnel.
- Through that funnel, the researchers controlled a consistent flow of air and airborne particles.
- To mimic the impact of breathing on the mask, the researchers created realistic to real-life conditions, with high humidity levels and temperatures.
- One crucial aspect is that the testing was conducted using a perfect fit.
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After the study, this is what the researchers concluded:
- After repeated washing and drying, although the fibres of the cotton squares started falling apart, it didn’t alter the mask’s filtering capacity.
- The only negative effect was that there was a slight increase in the inhalation resistance. This means that the mask became difficult to breathe through after washing and drying multiple times.
Good For Sustainability
Reflecting on the findings of the study, lead author Marina Vance said, “it is good news for sustainability.” "That cotton mask that you have been washing, drying, and reusing? It is probably still fine, do not throw it away,” she added.
- Since the start of the COVID-19 pandemic, 7,200 tons of medical waste is generated every day, much of which comprises of disposable masks.
- "We were really bothered during the beginning of the pandemic when going out on a hike or going downtown, and seeing all these disposable masks littering the environment," Vance said.
What Mask You Should Wear
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Apart from the reusability of the cotton masks, the study also pointed towards their effectiveness, that surgical masks, as well as cotton masks mounted over surgical ones, are better than cotton masks.
- As per the study, cotton masks filtered about 23% of the smallest particle size, which is 0.3 microns, on which the virus can travel.
- The effectiveness of surgical masks was much better as they filtered between 42-88% of the small particles.
- The filtration efficiency of cotton masks mounted over surgical masks was about 40%.
- KN95 and N95 masks were the best performers as they filtered out 83-99% of the tiny particles.
Although its efficiency is comparatively less, cotton masks are still good for those who prefer to use these soft, affordable, reusable, and environment-friendly masks. The only thing to ensure is that they should fit well to effectively filter out the dangerous airborne particles.
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