Disposable masks, washed and worn again, still protect better than a triple-layered cloth one, a group of New Zealand researchers say.
The study concluded that disposable masks could be put through a washing machine 10 times and still outperform three layers of cotton.
On the streets of central Auckland, many people have chosen a cloth mask over disposable ones, including Nora, who was wearing one dotted with colourful flower patterns.
"You don't need to waste [the mask] all the time... You don't have to throw [them] away and it's very fashionable, very cute," she said, adding that it's also more comfortable.
Nelson-based microbiologist Richard Everts said it was a "false benefit" to seek comfort over protection as some fabric masks have thin layers and may not fit well.
The research project lead said the performance of single-use commercial medical masks are the result of decades of research.
"We found that commercial masks, even when you wash them 10 times, were better than the fabrics - even when you had three layers of fabric, one on top of the other, the commercial masks were still better."
Everts said his team got a few brands of disposable medical masks and fired Covid-sized particles towards the fabric.
They found brand new medical masks stopped up to 98 percent of the particles. Then they washed them in eight different ways - the harshest being in a washing machine, or by using detergent, soap or bleach.
After 10 consecutive washes using those deep clean methods the disposal masks still filtered out about half of the particles.
Everts explained how to wash the disposable masks.
"The best way to do is a way that includes water to clean away all the biological material, and preferably warm or hot water, because that will get rid of bacteria and viruses and kill them and then you have to let it dry. The drying will kill any virus that is still there and most bacteria."
The researchers then fired particles at single-layer fabric such as cotton. Washed or unwashed - the result was the same - cotton only stopped 10 percent of the particles. When triple layered, the material still only hit 40 percent.
Everts said cloth masks can be more effective when a proper filter layer was inserted.
Senior research fellow at the University of Otago Wellington, Lucy Telfar Barnard, also worked on the mask study.
She said in a medical setting single-use masks should be treated as immediately disposable after first use but for an average consumer, it's safe to wash and reuse. She said it's also a greener approach.
"I absolutely recommend people to wash their disposable masks. There's an environmental impact from just disposing of them. They are made generally of synthetic materials, so they'll take a little while to break down," she said.
Barnard said a well-fitted mask is as important as the material.
"It's that combination of fit and filter which really is doing the work. If you've got a poorly-fitting mask then then it really cuts down the effectiveness of it."
Epidemiologist from the University of Otago, professor Michael Baker, says many masks on sale are not up to standard and should be banned from sale. He said a national mask strategy is needed, and it should cover two areas.
"One is that it gives really clear guidance about what mask to use, when to use them and where to use them and the second thing it will do is that it would set national standards for masks so that you know that when you went to buy a commercial say a fabric mask, a reusable mask, you'd know that it was fit for purpose."
Baker said it should also be made clear what criteria homemade masks need to meet.
In a statement, the Ministry of Health said that in the healthcare setting, washing and drying of medical masks for healthcare workers is not recommended.
"‘Single-use’ medical masks have not been designed or intended to be reprocessed, as the integrity of the mask can be reduced," it said.
"Consumers choosing to re-process this type of mask need to be aware that, as with other masks, they have a finite life span and it is important to check and follow the manufacturer’s re-use recommendations."