Cold plasma inactivates airborne virus

Cold plasma has been found to provide a more efficient method of sterilising air for medical procedure environments, meaning it could one day replace the surgical mask.

University of Michigan engineers passed an airborne virus through nonthermal plasma inside a prototype reactor. They were able to inactivate 99.9% of the test virus from the airstream at a pig farm, rendering it virtually harmless.

Krista Wigginton, U-M professor and co-author of the technique said: “The results tell us that nonthermal plasma treatment is very effective at inactivating airborne viruses. There are limited technologies for air disinfection, so this is an important finding.”

[caption id="attachment_85540" align="alignleft" width="228"] Cold, or nonthermal, plasma (NTP) is partially ionized gas where the energy is stored mostly in the free electrons and the overall temperature remains low. It has potential as a decontamination approach in various areas of food, medical and healthcare sectors. Professor Clack said: “It’s very similar to a flame, it’s just it doesn’t have a high temperature.”[/caption]

To inactivate the test virus, U-M scientists pumped a model virus that's harmless to humans into flowing air as it entered their nonthermal plasma reactor, which contained borosilicate glass beads in the shape of a cylinder.

When pathogens in the air stream flowed through spaces between the beads, they were oxidised by unstable atoms, leaving a virus that has diminished ability to infect cells.

Co-author Herek Clack said: “In those void spaces, you're initiating sparks. By passing through the packed bed, pathogens in the air stream are oxidized by unstable atoms called radicals.

“The most difficult disease transmission route to guard against is airborne because we have relatively little to protect us when we breathe,” he said.

This technique could be harnessed to replace the traditional surgical mask, which operates using only filtration for protection. Existing sterile air technologies that go a step beyond the surgical mask by sterilising surrounding air, such as ultraviolet irradiation, can’t sterilise as quickly or thoroughly as cold plasma.

The U-M team are testing their reactor on ventilation air streams at a livestock farm near Ann Arbor to tackle the threat of contagious diseases such as avian influenza.

They published their technique and findings in the Journal of Physics D: Applied Physics.