FFP2 respirator masks offer superior protection against Covid-19 than cloth masks

As the UK lifts the legal requirement for face masks in most indoor public spaces in England, new research from the University of Surrey and the University of Bristol has shown that FFP2 (Filter Mask ) are generally five times more effective at filtering particles that carry the Covid-19 virus than cloth masks.

The new research, published in Fluid physics, details how the Surrey-led research team performed confocal microscopy to take three-dimensional images of woven fabric, the type of material typically used to make cloth masks. They then used the image to perform Lattice Boltzmann simulations of airflow through tissue, a common technique used by physicists to analyze fluid dynamics.

The results of the simulations allowed the team to calculate the filtration efficiency for particles of one micrometer (one thousandth of a millimeter) and larger in diameter. For particles with a diameter of 1.5 micrometers – the typical size of Covid-carrying particles – the team estimated that the woven fabric is only 2.5 to 10% efficient, because most of the flux air is channeled through relatively large spaces between the threads of the fabric. Multiple layers of fabric improve efficiency roughly linearly, meaning three-layer fabric masks are up to 30% efficient, but this is still poor compared to the material used for FFP2 masks, which is generally more than 90% efficient.

While advice to wear face coverings in crowded public places remains in effect and many people are likely to choose to continue wearing them in other settings, it also remains important that people are able to make choices. enlightened on the types of face coverings to wear. . Our research shows that simply switching from a cloth mask to an approved FFP2 respirator greatly improves protection and reduces transmission. The woven fabrics used for cloth masks help disrupt airflow when people talk, sneeze and breathe, reducing the distance emitted germs travel, but they are less effective at filtering than FFP2 masks.

Dr Richard Sear, Study Lead Author, Department of Physics, University of Surrey

Jake Wilkins, an undergraduate physics student when he helped write the research, said:

“I feel lucky to see the results of my work published and to know that I am contributing to a better knowledge. FFP2 masks are so much better than cloth masks at filtering out dangerous particles like Covid-carrying particles. If we wear FFP2 masks to medical appointments, it could help protect NHS staff, the majority of whom are asked to use Type II surgical masks. These are good, but not as good as FFP2 masks. However, I would like to see progress towards recyclable masks because the environmental cost of air filtration is high.


Journal reference:

Rios de Anda, I., et al. (2022) Modeling the Filtration Efficiency of a Fabric: The Role of Multiple Length Scales. Fluid Physics. https://arxiv.org/abs/2110.02856.

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