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.

Microbiologist Richard Everts says it's a "false benefit" to seek comfort over protection as some fabric masks have thin layers and may not fit well. Photo / RNZ
Microbiologist Richard Everts says it’s a “false benefit” to seek comfort over protection as some fabric masks have thin layers and may not fit well. Photo / RNZ


The research project lead said the performance of single-use commercial medical masks are the result of decades of research.

Everts said his team got a few brands of disposable medical masks and fired Covid-sized particles towards the fabric.

They found new medical masks stopped up to 98 per cent 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 disposable masks still filtered out about half the particles.

Everts explained how to wash the disposable masks.

“The best way 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 per cent of the particles. When triple layered, the material still only hit 40 per cent.

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 disposed of 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 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 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.


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