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8 October 2021

Wash your disposable masks, experts say

Group of Kiwi researchers say you can wash a disposable mask 10 times and they still filter better than cloth ones.  

Disposable masks, which we’ve been advised to throw out after each wear, can actually be washed and reworn, a group of New Zealand researchers has found.  

In good news for both the environment and our wallets, a study by the researchers, which includes infectious disease experts, found disposable masks washed 10 times did a better job at filtering than cloth masks.

The masks were washed in one of eight different ways, with washing in warm water the method that had the least effect on filtration rate.

Dr Richard Everts washes his disposable mask under warm water, the best method according to the paper he was the lead author of.
Dr Richard Everts washes his disposable mask under warm water, the best method according to the paper he was the lead author of.

Nelson-based infectious disease specialist physician and microbiologist Richard Everts pulled the group together more than a year ago to carry out the study. He’s excited to finally be able to tell people it was OK to not throw out their disposable masks after one use.

“I was working in Vanuatu when I first heard about Covid-19 spreading through China and I was thinking ‘this is not going to be good here’,” Dr Everts said.

“They had very few masks at that time for a population of over 300,000 and then when new supplies did arrive, I knew they weren’t going to be able to use them once and throw them out. So that got me started with the whole idea of how long masks can be used for.”

Dr Everts said he wasn’t surprised that disposable masks held up well.

“They’re an extremely refined product. They’re strong, they’ve got three layers and I suspected they would withstand some washing.”

In the study, three disposable mask brands that complied with the European standard, were washed eight ways.

After they had been washed 10 times, these standard-compliant disposable masks had better filtration efficiency than new non-compliant masks and fabric samples, even when the fabric was triple-stacked.

After warm water, the least damaging methods were soaking in hot water and boiling water. Filtration efficiency was affected more when they were washed with dishwashing liquid, hand soap, bleach and in a washing machine.

“People in developing countries and people using masks in the community in New Zealand are already doing this and so we want to get the message to those people that it’s OK and they are best to avoid soap or detergent,” Dr Everts said.

He said massaging the mask in warm water would remove biological material, such as mucus and saliva, and hanging it up to dry overnight was what disinfected it. If you were planning to share the mask with someone else, you should submerge it in boiling water for a few minutes before hanging it to dry.

He said using soap, dishwashing liquid or bleach affected the electrostatic charge on a mask’s middle layer, making it less effective but still better than cloth masks.

Dr Everts said from an infection point of view he’d rather see people wearing disposable masks than cloth.

“Some cloth masks are sewn by well-meaning people and they’re better than no mask, but there’s a lot of published research that shows most cloth masks are very poor at stopping viruses. Based on our research and others from overseas, a good quality commercial medical mask washed in warm or hot water 10 times will still be better than 90 percent of the cloth masks out there.”

Co-author Lucy Telfar Barnard, an epidemiologist at Otago University in Wellington, also said she’d prefer people wore a disposable mask than a cloth mask, but only if it fits well.

“I don’t want to say people are wrong to be wearing reusable, because if you’ve got one that’s three layers and it fits you well it will be better than one that doesn’t fit. But if you don’t have one that fits well and you’re looking at what to buy in the future, if you can get a good fit with a surgical mask, I’d prefer people to do that,” Dr Telfar Barnard said.

She encouraged people to fiddle around with a disposable mask to get a good seal around the face. “The problem with disposable masks is it can be hard to get a good fit because they’re one size fits all, but you can get tricky with the elastics and tucking bits in.”

Dr Everts said healthcare workers or people in high-risk situations should always wear a new face mask. He said employers of people in essential services should be supplying their staff with new, high-quality disposable masks. The Ministry of Health recommends disposable masks be discarded after one use.

Dr Telfar Barnard said most masks sold in New Zealand were compliant with the European standard or another standard from around the world, which showed they had been tested and were good quality.

See our mask buying guide for more information on choosing a mask.

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