Article image

Virus lifespan and transmission boosted by high CO2 levels

Scientists at the University of Bristol have made a significant breakthrough in understanding how certain viruses, including SARS-CoV-2, spread through the air. The findings reveal that carbon dioxide (CO2) levels play a critical role in the lifespan and transmission of airborne viruses.

CO2 increases virus lifespan

Viruses are known to spread through tiny droplets expelled when we breathe, sneeze, or cough. These droplets carry viruses from one person to another through the air. However, recent research explores how the chemical makeup of droplets influences the lifespan of a virus.

Under normal circumstances, the fluid in these droplets is slightly alkaline. This alkalinity works against virus survival, deactivating viruses gradually like a microscopic defense mechanism.

The study introduces a critical variable: CO2. When CO2 is present in the air, it interacts with the moisture in the droplets, acting like a mild acid. This interaction is crucial because it decreases the natural alkalinity of the droplets by making them less alkaline.

In environments with high CO2 levels, like poorly ventilated rooms or crowded spaces, the acidity in droplets increases. This disrupts their natural self-cleaning process.

By reducing alkalinity, CO2 creates more favorable conditions for viruses. This allows them to stay infectious longer. The extended virus lifespan increases the chances that more people will be infected.

Significance of the CO2-virus connection

This research provides valuable insights into how and why viruses are transmitted more effectively in certain environments, highlighting the following key points:

Crowded, poorly ventilated spaces

These areas are often found in public transport, offices, or indoor events. They tend to have high CO2 levels because many people breathe in close proximity. The study suggests that high CO2 levels decrease the natural alkalinity of respiratory droplets and prolong the life of viruses within them.

This chemical shift likely leads to higher virus transmission rates. Crowded spaces that are poorly ventilated are known hotspots for spreading diseases.


Fresh air has always been considered beneficial for respiratory health, but this study quantifies just how crucial good ventilation is in controlling virus spread. By introducing outdoor air, we can effectively dilute the concentrations of both CO2 and airborne viruses indoors.

This reduces the overall viral load and speeds up virus deactivation. Improving ventilation or opening windows enhances public health safety in crowded spaces.

Climate change

The broader environmental context of this research cannot be ignored. As global CO2 levels continue to rise due to human activities like burning fossil fuels and deforestation, the implications for public health could be profound.

Increased atmospheric CO2 could mean that even outdoor environments might someday mimic the less alkaline conditions typically found in crowded, poorly ventilated indoor spaces.

This could increase the stability and transmissibility of respiratory viruses worldwide. It highlights a dire need for robust public health strategies to address both environmental and health policy challenges. This approach is crucial to mitigate the risks of future pandemics.

Implications of CO2-virus connection

The study has far-reaching implications for public health measures to help prevent airborne virus transmission.

Enhanced ventilation

Indoor air quality emerges as a pivotal factor in mitigating the transmission of viruses. Enhancing ventilation is essential, particularly in shared and frequently occupied spaces such as offices, schools, and public transportation. This can be achieved through several methods:

  • Natural ventilation: Simply opening windows can significantly improve air exchange and reduce CO2 levels, making this one of the most accessible methods.
  • Mechanical ventilation: Upgrading HVAC systems to ensure they are not only circulating air but effectively replacing it with fresh air from outside.
  • Air filtration systems: Implementing HEPA filters or other air purification technologies can help remove viral particles from the air, complementing the dilution of CO2.

Monitoring CO2 levels

Monitoring CO2 levels in indoor environments provides a practical way to assess air quality in real-time. High CO2 levels often indicate inadequate ventilation, signaling a higher risk for prolonged virus transmission in these spaces.

Therefore, CO2 monitors can serve as an early warning system, prompting necessary adjustments to ventilation practices, particularly in crowded or enclosed areas like conference halls and classrooms.

Continued importance of masking

Physical barriers such as masks remain crucial in controlling the spread of respiratory viruses. Masks effectively block a significant portion of respiratory droplets from being inhaled or expelled, thereby reducing the overall risk of virus transmission.

This protective measure is particularly important in settings where ventilation improvements are impractical or insufficient.

While the research is ongoing, the findings from this study contribute to a new understanding of airborne virus lifespan and transmission in the face of rising CO2 levels.

“We are now gaining a much more complete picture of the role exhaled respiratory aerosols play in transporting infectious viruses between people and the mechanisms that control their survival,” said co-author Professor Jonathan Reid.

The study is published in the journal Nature Communications.


Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and


News coming your way
The biggest news about our planet delivered to you each day