There are a lot of ways to kill viruses, but it’s not that easy to kill them in the air. For the most part, if you want to prevent viruses from infecting someone, or from entering a room, for example, you use a face mask or air filters. In some cases, such as in laboratory spaces, ultraviolet light is used to kill off pathogens. Of course, in some cases of specific disease-causing viruses, vaccines can be used in people, which safely trains your immune system to recognize and kill the viruses.
Now, researchers at the University of Michiganhave shown that dangerous airborne viruses can be killed “on-the-fly” when exposed to so-called “cold plasma,” or energetic, charged air molecule fragments. They published their work in the Journal of Physics D: Applied Physics.
“The most difficult disease transmission route to guard against is airborne because we have relatively little to protect us when we breathe,” stated Herek Clack, UM research associate professor of civil and environmental engineering.
The researchers evaluated the virus-killing speed and effectiveness of nonthermal plasma, that ionized particles created around electrical discharges, such as sparks. They found the reactor inactivated or removed 99.9% of a test virus, mostly because of inactivation. The reactor had borosilicate glass beads packed into a cylinder. They initiated sparks between the void spaces and passed a model virus via flowing air into the reactor.
“In those void spaces, you’re initiating sparks,” Clack stated. “By passing through the packed bed, pathogens in the air stream are oxidized by unstable atoms called radicals. What’s left is a virus that has diminished ability to infect cells.”
The authors noted in their paper, “Outbreaks of airborne infectious diseases such as measles or severe acute respiratory syndrome (SARS) can cause significant public alarm. Where ventilation systems facilitate disease transmission to humans or animals, there exists a need for control measures that provide effective protection while imposing minimal pressure differential.”
The researchers also evaluated the amount of viral genome in the air samples. They determined that more than 99% of the air sterilizing effect of the reactor was caused by inactivating the virus, while the rest was the result of filtering the virus.
“The results tell us that nonthermal plasma treatment is very effective at inactivating airborne viruses,” stated Krista Wigginton, assistant professor of civil and environmental engineering. “There are limited technologies for air disinfection, so this is an important finding.”
The research team believes that a parallel approach of filtration and inactivation of airborne pathogens would be a more efficient way of sterilizing air than current technologies, such as infiltration and ultraviolet light. Face masks usually only filter out viral particles and ultraviolet irradiation is a slower process and not as thorough as the nonthermal plasma appears to be.
The group has begun testing their reactor on a livestock farm near Ann Arbor, Michigan, using it to sterilize ventilation air streams. Animal agriculture is often vulnerable to contagious livestock diseases such as avian influenza or porcine reproductive and respiratory syndrome (PRRS) virus.
For example, in hog farms, air filtration is very important but is considered to be very expensive. Typically those systems use filtration, while others use a partial filtration or “bailout” system, in which air is 100% filtered at lower temperatures. But when the ventilation needs to move warmer air from outside, say from 70 to 80 degrees Fahrenheit, the air enters unfiltered.