Dangerous airborne viruses can be rendered harmless on-the-fly when exposed to 'cold plasma' -- a stream of energetic, charged fragments of air molecules, scientists have found.
The team from University of Michigan in the US hope to one day harness this capability to replace the surgical mask.
The researchers have measured the virus-killing speed and effectiveness of nonthermal plasmas -- the ionised, or charged, particles that form around electrical discharges such as sparks.
A nonthermal plasma reactor was able to inactivate or remove from the airstream 99.9 per cent of a test virus, with the vast majority due to inactivation.
Achieving these results in a fraction of a second within a stream of air holds promise for many applications where sterile air supplies are needed.
"The most difficult disease transmission route to guard against is airborne because we have relatively little to protect us when we breathe," said Herek Clack, research associate at University of Michigan.
To gauge nonthermal plasmas' effectiveness, researchers pumped a model virus -- harmless to humans -- into flowing air as it entered a reactor.
Inside the reactor, borosilicate glass beads are packed into a cylindrical shape, or bed. The viruses in the air flow through the spaces between the beads, and that is where they are inactivated.
"By passing through the packed bed, pathogens in the air stream are oxidised by unstable atoms called radicals. What's left is a virus that has diminished ability to infect cells," Clack said in a statement.
During the tests researchers also tracked the amount of viral genome that was present in the air.
In this way, researchers were able to determine that more than 99 per cent of the air sterilising effect was due to inactivating the virus that was present, with the remainder of the effect due to filtering the virus from the air stream.
This parallel approach -- combining filtration and inactivation of airborne pathogens -- could provide a more efficient way of providing sterile air than technologies used today, such as filtration and ultraviolet light.
Traditional masks operate using only filtration for protection. Ultraviolet irradiation can't sterilise as quickly, as thoroughly or as compactly has nonthermal plasma.
The team has begun testing their reactor on ventilation air streams at a livestock farm. Animal agriculture and its vulnerability to contagious livestock diseases such as avian influenza has a demonstrated near-term need for such technologies.