Disinfection | Researchers want to reduce germs with UV-C

The pretend classroom in Leipzig-Heiterblick looks remarkably similar to a real one – and yet there are several things that are different here: Instead of real high school students, 30 air-filled mannequins sit on the chairs, wearing T-shirts and electric heating pads underneath. This is intended to approximate the body temperature of a real person as closely as possible.

Hanging from the ceiling at several points are temperature gauges and narrow metal tubes through which air can be extracted and measured. Then, in the corners, for example, are devices that look like telescopes, which can suck in the air and treat it with UV-C radiation.

The supposed classroom is a new real-world laboratory on the premises of the lighting specialist NEL. Major Leipzig research institutions – the Leipzig University of Applied Sciences (HTWK), Leipzig University, the Helmholtz Centre for Environmental Research, and the Leibniz Institute for Tropospheric Research – have partnered with industry to build the nearly 200-cubic-meter laboratory. The project is being funded with more than 2.5 million euros by the German Federal Ministry of Education and Research.

The BeCoLe research project is investigating whether and how UV-C radiation can be used to reduce the exposure to pathogens in public spaces. Ventilation remains the simplest and most effective protection. However, not all public spaces—such as cinemas or theaters—allow windows to be opened. And in winter, it's often too cold for extended ventilation.

An alternative are mechanical filter systems, but these are often too loud. Researchers in Leipzig now want to find out how UV-C-based disinfection systems can be used to rid rooms of viruses and bacteria. UV-C radiation is a part of the ultraviolet spectrum with a wavelength between 100 and 280 nanometers. This radiation can kill bacteria and viruses – but it can also be potentially harmful to health, for example, to the eyes and skin.

Until now, UV-C radiation has been used in the food industry, such as slaughterhouses, explains Rüdiger Hennig of NEL. It is also used to disinfect drinking water. In Leipzig, the real-world laboratory is now testing how germs spread in a room and to what extent UV-C devices can reduce germ loads.

Right next to the supposed classroom at the lighting manufacturer NEL is a small room that the researchers jokingly call the "poison kitchen." This is where the self-developed atomizer is located, which can be used to aerosolize particles into the room. The researchers don't use real viruses, but harmless substitute viruses. This allows them to simulate various situations.

This could be the case, for example, where the teacher standing at the front of the classroom has coronavirus or influenza, and the aerosols are coming from there. How are the particles distributed throughout the room? What reaches the student in the back row and what reaches the student in the front? With the help of the real-world laboratory, researchers can now reliably measure and record this.

In Leipzig, researchers are currently testing the disinfection of the room using three UV-C-based systems. One looks like a skylight. It emits ultraviolet radiation toward the ceiling. The idea is that warm air rises, the germs are killed by the light, and then the germ-free air sinks back down.

Another system is located in the corner of the classroom. It looks like a telescope, draws in air, and then treats it with UV-C radiation. These models already exist in industry and are market-ready. If they work, they could be an alternative or supplement to infection control in public spaces in the future, for example, in the event of another pandemic. But given the many unanswered questions, in the end, nothing is as cost-effective as simply ventilating. dpa/nd