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A new study from researchers at UCL and UCLH has raised concerns about the unintended consequences of increased ventilation and air cleaning in hospitals, suggesting that these measures could sometimes exacerbate the spread of airborne viruses, such as SARS-CoV-2 or influenza.
The research, published in Aerosol Science & Technology, explored how mechanical ventilation and portable air cleaners (PACs) affect the movement of airborne particles in a hospital outpatient clinic. The study’s authors simulated various scenarios to track how viral particles, similar to those released by infected individuals, spread in the hospital’s air.
Using an aerosol generator and particle counters, the team monitored particle movement in a real-world clinic setting at UCLH in central London. They tested factors such as the positioning of ventilation devices, the placement of PACs, and the effects of closing doors on the movement of particles.
The findings were unexpected. While the use of built-in ventilation and PACs helped to reduce particle spread in some cases, there were also situations where these devices made things worse. In certain experiments, PACs increased aerosol spread by as much as 29% between neighboring rooms. In another case, mechanical ventilation systems caused particles to move across the clinic up to 5.5 times further than when no ventilation was used.
Professor Laurence Lovat, senior author of the study, explained, “The COVID-19 pandemic emphasized the risks of airborne viral infections in hospitals, leading to a greater reliance on ventilation systems and air cleaners. However, our study reveals that the way these devices interact with airflow can have unintended consequences. Each space is unique, and the airflow patterns are not always predictable.”
The researchers’ experiments included testing different configurations of doors, air cleaners, and ventilation systems. For instance, when room doors were closed, the spread of particles was significantly reduced. However, in some cases, larger PACs caused more particles to spread further by introducing their own air currents.
Dr. Jacob Salmonsmith, first author of the study, noted, “Changing the air more frequently may seem like a good solution, but our study shows that larger air cleaners can have a counterintuitive effect by causing unfiltered particles to move further than they would in still air.”
The study also highlighted the unpredictable nature of aerosol spread. In one experiment, rooms furthest from the aerosol source had much higher concentrations of particles when a PAC was in operation. In another, the nurses’ station—an area frequently visited by staff—showed particularly high concentrations of particles, raising concerns about the risk of healthcare workers being exposed to airborne infections.
While the findings raise alarms, they also provide valuable insights into how hospitals can improve their infection control strategies. The team is currently working on an AI system to simulate airflow patterns and optimize the placement of ventilation and air cleaning devices, potentially leading to more effective measures to reduce infection risks in healthcare settings.
Professor Andrea Ducci, another author of the study, stated, “Our experiments show that airflow dynamics can corral particles into specific areas, and we are working to identify simple, actionable interventions to reduce this risk.”
As the study progresses, its findings could help inform future policies on hospital ventilation standards, especially in light of the lessons learned from the COVID-19 pandemic.
Disclaimer: The findings of this study are based on laboratory simulations and may not fully reflect real-world scenarios. Further research and testing are needed to confirm these results and guide actionable changes in hospital ventilation systems.
