Do washing and drying reduce the filtering ability of reusable masks?  

People switched to different types of masks amid pandemic but were curious about the filtering ability of the cloth mask that they have been washing, drying and reusing. A recent study concluded that washing and drying cloth masks don't reduce their ability to filter out viral particles.
Created On: Sep 10, 2021 18:42 IST
Modified On: Sep 10, 2021 18:42 IST
Do washing and drying reduce the filtering ability of reusable masks?  
Do washing and drying reduce the filtering ability of reusable masks?  

Amid the ongoing COVID-19 pandemic, people were advised by the authorities to use face coverings such as surgical and coth masks to contain the spread of the deadly virus. 

Since then they have switched to different types of masks but were curious about the filtering ability of the cloth mask that they have been washing, drying and reusing.  A recent study concluded that reusing cloth masks don't reduce their ability to filter out viral particles.

What does the study say?

A study published in the journal Aerosol and Air Quality Research concluded that washing and drying cloth masks don't reduce their ability to filter out viral particles.

The research further confirmed that layering a cotton mask on top of a surgical mask provides more protection than cloth alone, provided that the mask properly fit on one's face. 

This is a piece of good news for sustainability because since the onset of the COVID-19 pandemic an estimated 7,200 tons of medical waste has been generated every day-- much of which is disposable masks.

Lead author Marina Vance, assistant professor in the Paul M. Rady Department of Mechanical Engineering said, "It's good news for sustainability. That cotton mask that you have been washing, drying and reusing? It's probably still fine--don't throw it away."

She further added, "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."

How the research was carried out?

A double-layered square of cotton was created and was put through repeated washing and drying (up to 52 times, the equivalent of a weekly wash for a year) and was tested between every 7 cleaning cycles.

The researchers mounted the masks on one end of the steel funnel and tested them using realistic to real-life conditions, with high humidity levels and temperatures to mimic the impact on the mask from our breathing.

While the cotton fibres of the masks started falling apart due to repetitive washing and drying, they didn't affect their filtration efficiency. Only their inhalation resistance slightly increased. 

It is to be noted that masks were not tested using real people and were instead exposed to air and airborne particles. Also, the test was conducted using a perfect fit in the lab-- no gaps between the mask material and the person's face.

Masks and their filtration efficiency

The study concluded that the cloth masks provide less protection than the surgical masks or a layered combination of surgical and cloth masks.

Cotton masks filtered out up to 23% of the smallest particle size (0.3 microns) on which the virus can travel. Bandanas filtered only 9% of such particles.  

Surgical masks filter out 42-88% of the tiny particles, and cotton masks on top of surgical masks have around 40% filtration efficiency. 

KN95 and N95 masks unsurprisingly performed the best, filtering out 83-99% of these particles.

The findings of the study remain useful for those who rely on cloth masks for their comfort, affordability and reusability. 

"I think the best mask might be the one that you're actually going to wear, and that is going to fit snugly against your face without being too uncomfortable," added Vance.  

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