Do UV lights really kill germs

Corona: lights on - virus dead?

With ultraviolet radiation against germs of all kinds. That is the business idea of ​​companies that offer disinfection systems based on UV-C radiation.

Instead of spraying chemicals around, they irradiate surfaces, water and air with UV-C light. This light is invisible, but powerful: Viruses, bacteria and other germs break within seconds if they are irradiated with it.

The radiation damages the genetic material and prevents pathogens from multiplying further.

This knowledge about UV-C is actually nothing new - radiation has been used for decades to disinfect drinking and bathing water, for example. The surfaces of ambulances and industrial conveyor belts are also cleaned using UV-C lamps. It also removes germs from the air in rooms.

With UV-C against corona?

Since SARS-CoV-2 became a new kind of pathogen in the world that can also be transmitted through aerosols in the air, UV-C disinfection has again been of particular interest.

In addition, autumn is just around the corner and the question arises as to how best to keep the air in classrooms or offices virus-free even during the cold season.

If you listen to the manufacturers of UV-C disinfection systems, then of course with their products. From a business point of view, they are already among the winners of the corona crisis.

Because demand has increased so, the Dutch company Signify, for example, produces eight times as many products as it did before the pandemic.

New UV-C lamps on the market

The company also launched a new UV-C lamp in the spring.

Up to now, lamps that are in operation while people are in the room at the same time have been shielded by a tight housing. With the Signify lamp, on the other hand, the radiation is directed upwards with the help of a reflector and forms a UV-C veil under the ceiling through which the air is circulated and thus disinfected.

Signify's UV-C lights on the ceiling of a waiting room

Before the crisis, the buyers of UV-C disinfection systems, especially for air purification, were mainly in Asia and North America. In Europe there are more concerns about how to use the technology safely, says Christian Goebel, UV-C expert at Signify.

Since the pandemic, however, a market has slowly developed in western Europe as well. And this although there is no recommendation from the Robert Koch Institute or the Federal Environment Ministry to use UV-C systems.

Risk of injury from UV-C radiation

The Federal Environment Agency (UBA) is also rather reluctant to use UV-C light in rooms where people are at the same time.

The managing director of the indoor air hygiene commission affiliated there, Heinz-Jörn Moriske, points out that UV light is harmful to health: "If these devices are then opened by people in the room for whatever reason and the lamp is still on, it can cause severe burns to the skin and burns to the eyes. "

Manufacturers are aware of the risks of UV-C, but still cannot understand the assessments of the various offices and institutes. "The technology has been tried and tested. Everyone knows that it helps. That is then just a question of using the technology safely," says Christian Goebel from Signify.

Safe handling is given when the disinfection systems are installed professionally. In addition, the people who are in the rooms in which UV-C technology is used should be briefed on how to behave. In this way, it can be ruled out that people accidentally come into contact with the radiation.

Demanding scientific research

Heinz-Jörn Moriske from the Federal Environment Agency is also critical of another point: The study situation is very thin. Signify recently demonstrated in collaboration with Boston University that UV-C radiation also kills the coronavirus on surfaces within seconds.

However, there is hardly any data on air disinfection using UV-C. How big the room is, how often the air flows past the UV-C lamps and how intense the radiation from the respective lamp is, everything has a huge impact on how much the germs in the room are damaged.

Since the air circulation in buildings differs from room to room and even from room corner to room corner, it is rather difficult to derive general statements from scientific studies in the laboratory.

The blue-colored UV-C haze in the picture is not visible in reality

According to Heinz-Jörn Moriske, there are also no studies on whether UV-C systems work more reliably than, for example, air purifiers with mechanical filters.

That is why he repeatedly emphasizes that the use of air cleaning devices with UV-C lamps or other filters is ultimately only a supplementary measure to ventilation through open windows: "That must not lead to people simply saying 'This is too cold for me now "I'm not ventilating. I have my air purifier on and it can do it." That is exactly the fallacy that we have to avoid. "

Companies want more pragmatism

Christian Goebel from Signify would like more pragmatism and openness from the authorities in view of the "size of the problem". In schools and kindergartens in particular, it is extremely difficult to avoid having many people in a confined space.

That is why UV-C disinfection systems are an absolutely sensible investment in such places, says Christian Goebel: "If you were to ask me now, 'Would I accept it if my son had a UV-C lamp in kindergarten?' I say 'yes'. "

  • Coronavirus AHA rules: How much distance can you please?

    But please keep a distance!

    These are the AHA rules as we know them: keep a distance of 1.5 to 2 meters (in Anglo-Saxon countries: 6 feet), observe hygiene and wear an everyday mask. But that does not do justice to the complex reality of how aerosols spread, wrote researchers from Oxford and London (UK) and Cambridge (USA) in an analysis published in the British Medical Journal at the end of August.

  • Coronavirus AHA rules: How much distance can you please?

    Like right now?

    British Prime Minister Johnson demonstrated the rules of distance in a classroom. But what does that mean exactly? Do you have to lie 1.50 meters between his fingertips and those of another potential human being? Actually that would be logical. But if a person measures 1.50 meters with two arm lengths, distances of a good 4.50 meters can quickly come together.

  • Coronavirus AHA rules: How much distance can you please?

    Or is it better to calculate in sheep's length?

    The Icelandic Sheep Breeders Association has set its own rules: two sheep lengths are appropriate to avoid infection. Whether the everyday mask is knitted from real sheep's wool? This young shepherd in Senegal sometimes pulls the animal's mutton legs long. Maybe he wants to find out how long a sheep is. The Icelanders already know: exactly one meter.

  • Coronavirus AHA rules: How much distance can you please?

    Natural spacers

    That’s how it works, of course. The standard length of a dog leash corresponds almost exactly to the applicable Corona rules. Could it be a coincidence that in the English-speaking world a "six-foot leash" is usually required for places where a leash is compulsory?

  • Coronavirus AHA rules: How much distance can you please?

    Where does the 2 meter rule actually come from?

    The team of authors led by professor of fluid dynamics Lydia Bourouiba writes that the rule is out of date. The German physician C. Flügge recommended this distance in 1897. Visible droplets that he had caught in this area were still contagious. Another study from 1948 showed that 90 percent of coughed strep streptococci in droplets did not fly further than 1.70 meters.

  • Coronavirus AHA rules: How much distance can you please?

    Two meters is not enough

    The 1948 study appeared in the American Medical Journal. It also showed that at least 10 percent of streptococci flew much further: up to 2.90 meters. Under such circumstances, the people on this meadow on the banks of the Düsseldorf Rhine might be safe - if every second district remained free. But wait a minute! We are not concerned with streptococci (bacteria) but with viruses.

  • Coronavirus AHA rules: How much distance can you please?

    Viruses spread through aerosols

    Viruses are much smaller than bacteria and can therefore float around for hours and also spread better in the room air. The researchers therefore recommend not only making the distance between two people a safety criterion, but also other factors: the ventilation of the room, whether people wear masks, whether they are silent, speak softly, or sing and shout.

  • Coronavirus AHA rules: How much distance can you please?

    Just don't sing or cough

    Numerous recent studies also show that real virus packages can be thrown up to eight meters when coughing. Loud speaking or singing also swirls some aerosols and droplets into the room. If, however, you only speak softly, like in a library, and if people are still sitting in the fresh air, the distances can be shorter again.

  • Coronavirus AHA rules: How much distance can you please?

    How long do I stay in the room?

    The length of stay in the contaminated room and how many people are in it are also decisive for the risk assessment. The researchers have developed a traffic light model from all of these factors. The clear result: In rooms with many people, you should only stay briefly, ventilate well, wear an everyday mask and speak softly.

  • Coronavirus AHA rules: How much distance can you please?

    A minute is enough to become infected

    Even very short contacts can be enough to pass on SARS-CoV-2. The US health authority CDC had to tighten its rules on October 21. A prison guard had previously been infected from prisoners with whom he had never been in contact for more than a few minutes. From now on, "close contact" is: less than two meters, at least 15 minutes but cumulative - over 24 hours.

  • Coronavirus AHA rules: How much distance can you please?

    You can also do this without a mask

    Here, however, the traffic light of the British-American research team is green: Without a mask, it is only safe outside, even over a long period of time, when there are few people around, everything is well ventilated and nobody speaks much. But will the 1.50 meters be enough?

    Author: Fabian Schmidt