A new study by University College London (UCL) researchers suggests that ventilation systems in hospitals, intended to limit airborne viruses, could sometimes actually exacerbate the problem. 

While air cleaners and mechanical ventilation reduce viral spread in some situations, the study found that in others, these systems inadvertently increased particle movement. For instance, large air cleaners created air currents that pushed unfiltered particles into neighboring rooms, boosting transmission by up to 29%. 

The unpredictable airflow dynamics inside hospitals, especially older buildings, make it essential to carefully consider the placement of ventilation devices. This research highlights the need for smarter airflow strategies to ensure infection control is both effective and efficient. 

The team is developing AI tools to improve the understanding of air particle behavior, potentially guiding future healthcare standards to reduce infection risks.

Dr Jacob Salmonsmith, first author of the study and an Honorary Research Fellow from UCL Mechanical Engineering, said: “The results of this experiment might seem counterintuitive if you take the view that changing the air in a room more often reduces the spread of viral particles. While it’s true that air cleaners do remove viral particles from the air and can reduce overall spread, they can also have unintended consequences. 

In particular, this experiment suggests that larger air cleaners, which have larger exhaust vents that introduce their own air currents, can cause particles that haven’t been filtered out to spread further than they would have if the cleaner wasn’t there. In any given space you have complex interactions between many different air currents, such as ventilation, doors closing and people’s movement. Our findings indicate that the whole picture needs to be considered when choosing when and where to introduce air cleaners."