Huge differences between effectiveness of best and worst face masks revealed by Which? tests

Which? is urging manufacturers and retailers to up their game on face coverings after the consumer champion’s lab tests revealed alarming differences in the effectiveness of widely-available reusable masks.

Which? found that the best performing face coverings were able to block more than 99 per cent of potentially harmful bacterial particles from penetrating the mask material – similar to the standard of surgical masks. But the worst only managed to filter out a paltry 7 per cent – allowing up to 93 per cent to escape.

With face coverings now an essential purchase and considered important for minimising the spread of coronavirus, Which?’s latest research looked at a range of popular brands and styles of face coverings and masks, including those sold by pharmacy chains, supermarkets, high street stores and online retailers.

Scientists tested for how well they filter bacteria, how breathable they are, and how they fare after multiple washes.

Three out of the 15 face coverings Which? tested performed so poorly that they were deemed a ‘Don’t Buy’. At the bottom of the table and earning the lowest scores overall were a face covering from Termini8 sold at Lloyds Pharmacy (£2), one from Asda (£3) and one from Etiquette (£3), which is sold at Superdrug.

All were lightweight and breathable as they were made with only one layer, but this affected their ability to filter potentially harmful particles, earning each mask only one star out of five in this category.

Which? awarded two of the products tested Best Buy status. The NEQI reusable face mask (£15 for 3), which is available from retailers including Boots and Ocado as well as Bags of Ethics Great British Designer face coverings (£15 for 3), available at Asos and John Lewis, were both considered comfortably breathable, earning the full five stars in this category without compromising on filtration (four stars out of five).

The lab tests revealed that masks with multiple layers are much more effective than single layer masks at filtering particles. However, Which? found that there was a clear trade off between breathability and how effective the mask was at filtering potentially harmful particles. In fact, the fabric masks that scored five out of five for filtration were also those that scored the lowest for breathability.

These included the Firebox reusable mask (£15), which is made with double-layered polyester and uses a double filter, Maskie Loop UV Sanitized reusable Face Mask (£6), which is made of three layers, and the Smart Mask (£14), which is also made of three layers and markets itself as the number one rated face mask in the UK, which all got one star for breathability. The AB Mask (£10), which is available at Boots, also received full marks for filtration but got two stars for breathability.

If a face covering isn’t breathable, it can get damp more quickly with condensation from trapped breath and might encourage people to adjust or remove their mask, especially if they wear glasses.

The Asos (£12) and AB Mask were the only two that avoided glasses steaming up and were rated highest for glasses-wearers’ comfort, with both scoring five stars in this category.

The Which? tests also revealed that almost all of the face coverings got better at filtering particles after being washed. Face coverings were re-tested after five hot wash cycles, and most improved, due to the fibres compressing.

While reusable fabric face coverings are not designed to block ultra-fine particles such as Covid-19 like a higher-grade medical respirator mask would, they are intended to help block larger droplets and aerosols breathed out by the wearer, who may be infected but asymptomatic.

The prevailing scientific thinking is that this should help protect the wider community by minimising exhalation of virus particles in enclosed public spaces.

Which? is urging manufacturers to use these findings as a basis for improving their products, while retailers should seek to ensure they are selling products that will effectively filter out potentially harmful particles. In the meantime, the consumer champion is encouraging consumers to research the best available options for themselves and their loved ones before making a purchase.

Natalie Hitchins, Which? Head of Home Products and Services, said:

“With face coverings now such an important part of daily life, they not only need to be durable and comfortable, but also provide effective filtration from harmful particles in order to keep us and others safe.

“Our results prove that there is a huge difference in quality between reusable masks sold in stores around the country and online. We would urge manufacturers to use our findings to up their game and improve their products – Until then it is worth taking time to research the best option for yourself and your loved ones.”



Notes to editors:


  • Which? has made the results of its face coverings test freely accessible to all. 
  • Pictures of the face masks are available on request


Which? has also previously investigated the efficacy of antimicrobial coatings on face masks. You can find our research here:


How to buy a face mask video.


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Should you wish to include a linkback in your copy, the following links will go live when the embargo breaks: 



  • Face masks full results page:  


  • Face masks buying guide:


How Which? Tests face masks


  • To get at bacterial filtration, Which? used an aerosol generator to shoot bacterial particles that were 3 micrometers in diameter at sections of mask fabric and see what percentage of bacteria made it through. 


  • To test breathability Which? measured the pressure required to draw air through each of the covering at a rate of eight litres a minute, which is two litres above the average breathing volume. 


  • To find out how well the masks would last with repeated use,testers put on and took off the masks 80 times, and to understand how comfortable the face covering is, testers with different face shapes were asked to assess the fit – looking for tightness, gaps and ease of adjustment. 


  • Which? also look for comfort while wearing and talking, and for glasses wearers – whether it made them fog up. 


Reusable face masks and coronavirus


  • It should be noted that coronavirus particles can be much smaller (as little as 0.1 micrometre in diameter), so what we are measuring is not the face covering’s ability to protect against coronavirus, per se. 


  • Face coverings are not medical devices and aren’t designed to block all particles down to these ultra-fine particles, like a higher-grade medical respirator mask would. 


  • Like basic disposable surgical masks, they are intended to help block larger droplets and aerosols emitting from the wearer, who may be asymptomatic, helping to create community protection by minimising exhalation of virus particles


Basic surgical disposable face masks


  • While disposable surgical masks must adhere to strict standards on filtration in order to be sold, there is no such binding standard for reusable fabric masks. However, surgical masks are single-use, non-recyclable products, so not really a practical solution for sustained daily use. They could also have a grave impact on the environment if millions end up in landfill.


  • At around 45p per mask, the cost of using just one disposable per day over the course of a year could be £164 – significantly more than Which?’s Best Buy reusable face coverings which come in packs of 3 for £15.


How to choose a reusable face covering 


  • Try to go for three layers, but at least two – our tests showed a clear difference between single-layer face coverings and those with a double or triple layer. 


  • Choose your material wisely  – tightly woven cotton is a good option – the homemade mask we tested did well on filtration – and worst performing masks were a single layer of mostly polyester. Ideally, a mix of different fabrics like cotton, polypropylene, and different types of polyester. 


  • Make sure it’s adjustable, or comes in different sizes – our testers rated face coverings higher for fit and comfort when they were adjustable, either by the ear loops and mouldable nose wire, or because the mask came in different sizes. Find out more in our face mask buying guide. 


ROR from Lloyds Pharmacy – seller of the Termin8 mask


“We take the quality and efficacy of the products we sell very seriously and work with our suppliers to ensure they comply with UK regulations and standards. We have confirmed with the supplier of the Termin8 mask in question that it is compliant with all necessary requirements as set out by the Department for Health & Social Care and the British Retail Consortium, for use as a face covering in numerous public settings as required by UK law.”




“We dispute the testing methods that have been used by Which? and are disappointed that the fabric Face Cover by our supplier Etiquette Super Mask has been given a ‘Don’t Buy’ rating because it has been tested against the EN 14683 standard for surgical masks and the CEN Workshop Agreement which is not an official standard. This product was clearly retailed as a fabric face covering and not a surgical mask – designed to help the wearer reduce the spread of a cold or virus, as per Government guidelines.”




“Product safety is our key priority and all of our George face coverings comply with and British Retail Consortium guidance and the Office for Product Safety and Standards. The covering that featured in this review was produced before the CWA17533 guidelines were published and is no longer on sale.”


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