Ninety-nine percent of airborne viruses can be eliminated if they are exposed to a “bombardment” of electrically-charged molecules (ions) and free radicals (highly-reactive molecule fragments), i.e. what the experts call non-thermal plasma. These results, which in particular are important for eliminating the possible contamination of highly-sensitive areas (like operating theaters or old people’s homes), were achieved by a team of researchers from the University of Michigan (USA), who published the results of their work in the Journal of Physics D: Applied Physics.

Viruses can be eliminated when air is made to pass through a special machine (a reactor), in which – to simplify it considerably – a succession of electric charges creates non-thermal plasma. The US researchers “contaminated” the air with viruses that are harmless to humans, and then channelled it through the reactor, also using an ozone-filtering system at the end of the procedure. They then measured the viruses remaining and realized that, thanks also to the final filtering, only 1% of the initial quantity remained. The antimicrobial power of the device is assured by the tiny sparks created by the charged particles when the current is passed, which destroy everything surrounding them, including viruses. The final filtration completes the disinfection.

The entire “cleaning” process lasts only a fraction of a second, and was achieved thanks to tools (those that cause the flow of ions and free radicals) that are found in many laboratories. “The results”, says Krista Wiggington, professor of civil and environmental engineering at the University of Michigan, “show us that the treatment is highly efficient and innovative. There are very few other techniques that are capable of disinfecting air. The new system is to be considered important also for this reason”.

The researchers are now trying out this non-thermal plasma disinfection in the ventilation systems of a large farm near the city of Ann Arbor in Michigan: a place particularly vulnerable to infectious microorganisms, which often are difficult to identify and to stop from spreading. Time will be needed to draw definitive conclusions, but the initial results are looking positive.

Credits: Robert Coelius/Michigan Engineering