A new study shows that keeping CO₂ levels low can help reduce the amount of infectious viruses in the air.
According to chemist Allen Haddrell from the University of Bristol (UK), opening windows can have more significant effects than people realize, especially in crowded, poorly ventilated rooms. Fresh air has lower CO2 concentrations, which causes viruses to become inactivated much faster.
CO2 Levels Affect Viruses
By measuring the ability of SARS-CoV-2 to remain infectious in aerosol form within droplets under various environmental conditions, Haddrell and colleagues found that CO2 levels in the air directly impact the stability of the virus.
Fresh air has lower CO₂ concentrations, making viruses inactivated much faster – (Photo: UKRI)
They employed a novel technique to measure the effects of temperature, relative humidity, and varying gas concentrations on suspended virus particles. CO2 levels in the atmosphere were measured at around 400 parts per million (ppm).
However, when enough people gather in a closed room, the concentration can surge to around 3,000 ppm. The research team discovered that the number of infectious virus particles at this high concentration can be up to 10 times greater than the amount of virus found in outdoor air.
“The high pH of droplets containing the SARS-CoV-2 virus when exhaled may be the primary reason for the loss of infectivity.
CO2 acts as an acid when interacting with water droplets. This causes the pH of the droplets to become less alkaline, resulting in the virus inside them being inactivated at a slower rate,” Haddrell explained.
Moreover, crowded environments in poorly ventilated spaces can exceed 5,000 ppm CO2. Chemist Haddrell noted that this relationship clarifies why super-spreader events can occur under certain conditions.
Climate Change Increases Virus Spread
Different strains of SARS-CoV-2 exhibit varying stability forms in the air. Therefore, although more research is needed to confirm the relationship between CO2 and other types of viruses, researchers suspect that this difference may explain why many respiratory viruses exhibit seasonal characteristics.
As the weather gets colder, people tend to spend more time indoors and are exposed to air with higher CO2 levels. Outdoor CO2 levels are also rising due to global warming. Recent forecasts predict that concentrations could exceed 700 ppm by the end of this century.
“The study also highlights the importance of global net-zero goals, indicating that even a slight increase in CO2, which is already rising due to climate change, can significantly improve the survival rate of viruses and increase the risk of virus spread,” Haddrell added.
Physical chemist Jonathan Reid from the University of Bristol concluded: “These findings could serve as the scientific basis for designing risk mitigation strategies to save lives during any future pandemics.”
The study has been published in the journal Nature Communications.
