Coronavirus: Face mask, face shield, FFP2, N95, KN95 — what's the difference?

A new British study shows that hospitals, where doctors and nurses observe strict hygiene and wear FFP3 masks were able to eliminate COVID-19 transmissions by almost 100 percent. That proves: Masks do work ― some more, some less. 

Since the onset of the Corona pandemic, most countries around the world have made masks mandatory for public spaces, mass transit and stores. In Germany, too, masks were compulsory in public buildings and offices, on trains and buses, and in cabs during the last Corona wave. At first, a self-made textile mask was sufficient, but later an FFP2 mask — known as KN95, N95, or P2 in other parts of the world was required. We explain what the different standards mean. 

Simple face mask

During most of last year, the regulation in Germany requires a simple face mask to be worn as a minimum requirement in most public areas. This is a piece of cloth that completely covers the mouth and nose. Even a bandanna or scarf would qualify. When you exhale, it inhibits the flow of air, and therefore, the distance that germs can travel. And this already significantly reduces the risk of infection for other people.

The purpose of such masks is not to protect the people wearing them from infection: They protect the people everyone else from the wearers' germs. Because the transmission is frequently caused by asymptomatic people, everyone is a potential virus carrier.

The logic behind the mask requirement is, therefore: if everyone complies, the overall risk of infection in society will fall.

Cloth masks should be changed frequently and washed in hot water to prevent viruses from surviving. 

Surgical masks 

Such medical face masks are the professional equivalent of cloth masks. They consist of thin disposable tissue and fleece and are used by doctors and assistants to primarily to prevent their patients on operating tables from being infected with germs and pathogens... If the wearer of the mask coughs or sneezes, for example, most of the droplets from the mouth and throat get caught in the mask. 

This only works if the mask is changed regularly and disposed of hygienically and safely. In surgery, doctors must change their masks at least every two hours. If a mask of this type is worn repeatedly, it quickly loses its effectiveness. 

During the pandemic, higher-quality masks with better filtration have become the standard practically everywhere in the medical profession. 

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How much protection does the mask provide?

Although the virus usually enters the body through the mouth or eyes, the hands play an important role in infections.

If you decide to wear a mask, you should probably also opt for protective goggles. The surgical masks, albeit less effective in keeping the viruses out, merely function as a constant reminder not to touch your nose with your hands when it itches. Neither should you rub your eyes.

FFP half-masks offer better protection

In addition to surgical masks, which look more like multilayer disposable kitchen towels, there are also half-masks with a real filter effect. These are more familiar to those who work in dusty environments or with aerosols. They are available either as disposable masks, usually made of strong pressed cellulose with a filter element and an exhalation valve, or as plastic masks in which a suitable filter is then inserted. 

In the European Union, these types of masks are divided into three FFP protection classes (filtering facepiece).

FFP1 

Although masks of protection level FFP1 are still better than surgical masks, they do not offer the desired protection against viruses. They are intended for carpenters, for example, who work at band saws with vacuum-extraction systems. Builders may wear them to catch the coarser dust that vacuum cleaners are unable to. Bricklayers can put them on before mixing cement with trowels, kicking up some dust.

FFP2/N95/KN95

FFP2 masks (equivalent to other international standards known as N95, KN95 and P2 masks) are becoming more and more prevalent for elder-care and nursing homes. Germany required them during the 2021 third wave in busses, trains and supermarkets. They provide a certain level of protection against viruses for the wearer, but should not be used when in contact with highly infectious patients.

Given the temporary shortage of hygiene materials during the first coronavirus wave in 2020, Germany's Robert Koch Institute announced at the time that medical staff could wear FFP2 masks rather than the standard FFP3 masks in infectious situations if FFP3s weren't available. Now there is no longer a shortage of high-quality masks for such critical workers. 

FFP3/N99/EN149/P3 

Only FFP3 masks (roughly equivalent to international standards such as N99, EN149 and P3) effectively protect the wearer from droplet aerosols, protein molecules, viruses, bacteria, fungi and spores, and even from highly dangerous dust such as asbestos fibres. Unlike simple surgical masks, such high-quality filter masks can protect the wearer — including from a highly infectious pathogen such as measles or tuberculosis. 

If a mask is needed — it needs to be the right one 

Protection only works if many other protective measures are taken at the same time: Strict hygiene when putting on a mask, protective goggles, gloves and plastic aprons, proper disposal of possibly contaminated disposable items, and regular handwashing. In addition, the surroundings must always be systematically disinfected. 

These masks — together with all other protective clothing — are therefore used in quarantine stations, for example, where patients who are already infected are cared for. 

What is the benefit of double-masking?

Wearing one mask on top of another is referred to as double-masking. Usually, you first put on a surgical, or FFP2, mask and then a tight-fitting cloth mask on top of that. It is important that the cloth mask fits so well that it is airtight at the edges. The idea behind this: To prevent air from flowing in or out past the mask.

The U.S. Food and Drug Administration (CDC) has conducted tests with double-masking and concluded that it can reduce the risk of infection by another 95 percent compared to a simple mask. However, it only works if used consistently. Also, wearing a tight-fitting double mask over a long period of time is significantly more uncomfortable than simply wearing a single mask.

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Problems with obligatory use of FFP2 masks

A legal requirement to wear FFP2 masks in supermarkets or public transport could cause all kinds of problems, both in implementation and control.

Though it is clear that FFP2 masks provide better protection than surgical or cloth masks, they only do so if they are used correctly. All masks of that kind are disposable.  Even if it is possible to sterilize them in an oven at 80 degrees Celsius (176 F), they can only be reused a few times.

The German Federal Institute for Occupational Safety and Health (BAUA) for example, emphasizes that reuse is "generally not intended" and may only be indicated or use in the event of an "acute shortage."

Most people will probably not buy a new mask every time they travel by train or bus or go shopping — especially as the already-high prices for quality masks are likely to rise as mask requirements are increased and market shortages result.

It seems more likely that many people will then buy only one or a few masks to comply with the formal legal obligation. They could then wear these for weeks or months — even without sterilizing them, especially since this is impossible to control. In that case, it might prove more hygienic to wear cloth masks that are regularly washed.  

Higher respiratory resistance — occupational health and safety requirements

Advocates for workers will be keen to ensure that occupational health and safety is maintained.

The fact that the masks have a higher breathing resistance than simple surgical or fabric masks plays a role here. According to the occupational health and safety rules in force in Germany, healthy employees may only wear the masks for 75 minutes at a time. After that, they are entitled to a 30-minute break.

The German Social Accident Insurance also stipulates that an individual risk assessment, which may include an occupational medical examination, is a prerequisite for the use of particle-filtering half masks.

People with preexisting conditions or disabilities such as respiratory diseases or reduced lung capacity are also often unable to wear particle-filtering masks for medical reasons.

Other approaches for better masks 

In addition to the three certified FFP mask types, there are other concepts for masks that have an antiviral effect. However, these would not meet formal regulatory requirements if FFP2 masks become obligatory in public spaces. Even if they were found to be effective, they would lack the necessary certification.

One such idea is to take advantage of the germicidal effect of copper. This is also used by hospitals, where you can find copper door handles to minimize infections. One manufacturer produces masks with a fine copper mesh as filter material.

Another approach for home use is to spray citric acid on a face mask. Phil Sadler, a mechanical engineering expert at the Arizona Controlled Environment Agricultural Center promotes this idea on YouTube.

It has been known for some time that citric acid can protect against noroviruses, which cause stomach and intestinal diseases. For example, using lemon juice when eating mussels can protect a person from norovirus infection.

US hygiene products manufacturer Kimberly-Clark experimented with citric acid-based antiviral facial tissues in the 1980s and 1990s with the intent to counter seasonal colds and flu. Sadler told DW that 41 years ago he also participated as a volunteer in a related research project at McMurdo Antarctic Station. Over the past 30 years, citric acid has also been used to some extent in N95 standard masks produced in the US as an antiviral agent. 

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Best protection: Don't forget to wash your hands

All masks and goggles are of little use if the most important hygienic principles are neglected. For example, if you come home after a long bus or train ride, where you touched handrails and handles, take off the mask and scratch your nose, there was no point in wearing the mask.

If you have been typing on the computer keyboard all morning at the office and then go to lunch without washing your hands first, you take a considerable risk. Then, wearing a mask at the computer workstation would have been of little use either. 

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And what about tear gas?

Demonstrators often also wear a variety of different protective masks — from simple surgical masks to half-masks with filters.

Surgical masks are probably only effective for concealing demonstrators' identities. However, when the police fire tear gas grenades that spray an aerosol, only FFP3 filters can provide some protection. To prevent the tear gas from getting into the eyes, airtight protective goggles are absolutely necessary. 

Occupational safety filters from the hardware store do not offer any real protection. A proper full-face gas mask with a military NBC filter would do the job.

And, of course, this also provides good protection against viruses. But in everyday life, nobody wants to walk around like this.

 (This article by author Fabian Schmidt was originally published on Deutsche Welle.)