Berlin - More and more people now wear FFP2 masks while shopping to protect themselves and others from Sars-CoV-2. With concern rising about the more contagious British variant of the coronavirus, politicians called for FFP2 masks to become compulsory nationally. Bavaria already requires FFP2 masks - in public transport and shops. Berlin hasn't gone as far: as of 24 January, a "medical" mask (including both surgical and FFP2) must be worn.

But how do FFP2 masks differ from cloth masks? What is the best way to wear them and how can they be cleaned? Below, we try to answer the most common FFP2 questions.

Reduced risk of infection

It is now well known that Sars-CoV-2 is primarily transmitted through droplets and aerosols. Several studies have shown that basic cloth masks - whether homemade or purchased - can reduce this kind of transmission. They prevent droplets and aerosols from spreading. However, the protection they offer the wearer is limited.

Respirators, also called FFP masks, protect against aerogenic transmission but can also significantly minimise the risk of infection for the wearer. German health minister Jens Spahn nevertheless urged caution: "Even FFP2 masks do not offer 100 per cent protection against the coronavirus. But they significantly reduce the risk of infection."

FFP stands for "Filtering Face Piece". The masks are made of hardened multi-layer paper or fabrics and contain filters. These masks come in three protective classes - FFP1, FFP2 and FFP3. The lowest-class mask, FFP1, protects mainly against non-toxic dusts. The FFP2 mask is suitable for protection against harmful solid and liquid dusts, smoke and aerosols. It also provides protection against airborne infectious agents. FFP2 masks are especially effective in filtering particles out of inhaled or exhaled air.

FFP3 masks are recommended for handling carcinogenic substances and pathogens such as viruses, bacteria and fungal spores. They are mostly used by medical personnel.

Tight fit a must

FFP masks must be worn correctly and changed often. They must fit very tightly to the face and sit some distance above the mouth and nose. People with beards are advised to shave. Optimal filtration only occurs when there is an airtight fit to the skin. You can tell if an FFP2 mask fits properly if the mask collapses slightly when you inhale.

FFP2 masks, which are standardised throughout Europe, filter out at least 95 per cent of particles. Some FFP masks have a valve to facilitate inhalation and exhalation. However, this has drawbacks: through the valve, the mask wearer can contaminate his or her environment with exhaled droplets. This is because the masks with an exhalation valve only filter inhaled air and therefore offer less protection to others.

FFP2 masks make breathing more difficult

When using an FFP2 mask, breathing is more difficult due to the built-in filter. The additional strain on the respiratory muscles is comparable to breathing through a straw and can result in shortness of breath - so you should think carefully about when and for how long you want to wear the mask.

Check the CE marking

Demand for FFP2 masks is rising, so there is a risk that uncertified masks could appear on the market. Pay close attention to the labelling. Particle-filtering masks (FFP2/FFP3) are certified because they are used in health care. Anyone who wants to buy such masks should look for the combination of the CE mark and four numbers on the packaging, advises certification body Tüv Nord.

If the masks meet the criteria of the corresponding test standard (DIN EN 149:2009-08), the packaging is given a CE mark and a four-digit number. This provides information about the certifying institute.

Can FFP2 masks be cleaned and reused?

FFP2 masks can be bought in pharmacies, drugstores and on the internet. They usually cost between five and six euros a piece – a pretty high price for a mask that is intended for single-use. Which raises the question of whether the masks can be cleaned at home for re-use. Germany's Robert Koch Institute advises against it because the filter could be damaged and the mask could lose its function as a result.

Nevertheless, scientists around the world have conducted several studies to determine whether the protective masks can be cleaned and reused. The main focus was on the following criteria: Are pathogens killed? Does the mask still fit? Is filtration affected? The tests focused on different cleaning methods:

Heat: In March 2020, the German government's corona crisis team advised exposing the masks to dry heat between 65 and 70 degrees Celsius for at least 30 minutes. We now know that this is not enough to kill the viruses. "At 65 to 70 degrees Celsius, it cannot be safely ruled out that pathogenic microorganisms remain on the masks after the process," the German Society for Sterile Supply warned in a statement in August.

Researchers at the Münster School of Health have found in studies that "Sars-CoV-2 on and in FFP2 masks remains infectious at 70 degrees Celsius after more than an hour. Only at 80 degrees Celsius dry heat is no infectious coronavirus detectable after 60 minutes." The scientists provide the following tip: First let the mask air-dry for a day. Then preheat your oven to 80 degrees Celsius (top and bottom heating), place the FFP2 mask on baking paper and then place it in the oven for 60 minutes. "The mask should only be reprocessed five times in this way and then disposed of in household waste," the researchers write.

Pathogens of the nose, throat and skin flora can still be present on the mask despite such heat treatment. Therefore, it is important that a mask is only ever reused by the same person.

Vapour: In hospitals, medical supplies are sterilised with hot steam. Is this a viable option for cleaning FFP2 masks? And how hot should the steam be? The German Society for Hospital Hygiene advises exposing masks to steam at 121 degrees Celsius for about 20 minutes. However, this only applies to hospital items that can be sterilised in a special vacuum process.

Sibylle Anderl, host of the FAZ newspaper's science podcast, shared a method of home sterilisation of FFP2 masks by steam. She refers to a study published last April in the Journal of Medical Virology. For their experiment, scientists packed the masks in airtight plastic bags or a stainless steel box and placed them in boiling water for about five minutes. This keeps the respirators dry, exposed to the heat but not damaged by it. Using this method, the masks can be reused for about seven to ten days - as long as they are not otherwise damaged and are cleaned regularly, the article says.

Disinfection with hydrogen peroxide: A study commissioned by the US Food and Drug Administration (FDA) showed that cleaning with hydrogen peroxide vapour might be possible. In the trial, the respirator mask retained its function but had lost its form. A similar study in the Netherlands concluded that the method was effective for two decontamination cycles without deformation. However, scientists wrote in the journal Plus One that bleach would severely destroy the mask's filters.

Hydrogen peroxide should be handled very carefully. In more concentrated form, the chemical can be corrosive to the skin, mucous membranes and eyes. A harmful concentration can remain on the mask for days after cleaning and could be toxic.

Photo: imago images / Frank Sorge
More and more people in Berlin are wearing FFP2 masks.

Ethanol, disinfectant spray, washing machine: Chemical methods that involve immersing the FFP2 mask in liquid ethanol are also not recommended. This causes the masks to lose their protective function. Disinfectant spray is also not suitable, according to the Robert Koch Institute. There is no guarantee that 100 per cent of viruses and germs are killed. Since the filtration performance of FFP2 masks is reduced when they are exposed to moisture, Tüv Nord also advises against washing them. This lowers the level of protection.

Ultimately - and this is a very unsatisfactory answer - everyone must decide for themselves how often they use an FFP2 mask and whether they try to clean it. What is certain is that the respirators minimise the risk of infecting oneself and others with the coronavirus. It is important that the mask completely covers the mouth and nose and fits tightly.

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