Study Finds That Ventilation Systems and Air Cleaners in Most Hospitals Are Actually Spreading Viruses Further

Thailand Hospital News: Recent research conducted by University College London (UCL) and University College London Hospitals NHS Foundation Trust (UCLH) has revealed that ventilation systems and portable air cleaners (PACs), commonly used in hospitals to prevent the spread of viral infections, might have unforeseen effects. Instead of containing airborne particles, these systems could inadvertently facilitate their movement within hospital environments.


Study Finds That Ventilation Systems and Air Cleaners in Most Hospitals Are Actually Spreading Viruses Further

Study Overview
The study aimed to understand how built-in mechanical ventilation and PACs influence the dispersion of airborne particles. These particles mimic those exhaled by individuals with respiratory infections like COVID-19 or influenza. Researchers simulated various scenarios in a typical hospital outpatient clinic at UCLH in central London. They used an aerosol generator and particle counters to monitor particle movement across different rooms and settings. Scenarios included assessing particle travel to adjacent rooms, throughout the clinic, and from one room to another on the opposite side of the clinic. Factors such as door positions and the placement of ventilation systems and PACs were also evaluated.
 
Key Findings
The findings were intriguing. While built-in ventilation and PACs reduced particle spread in certain situations, in some experiments, PACs increased aerosol dispersion by up to 29% between neighboring rooms. Additionally, built-in ventilation systems potentially amplified aerosol movement across the clinic by up to 5.5 times compared to scenarios without ventilation.
 
Professor Laurence Lovat from UCL Surgery & Interventional Science and UCLH commented, "The COVID-19 pandemic really highlighted the risk of picking up airborne viral infections in hospitals, which naturally led to efforts to reduce this risk. In many hospitals, the use of ventilation systems and portable air cleaners has increased." He emphasized the complexity of airflow patterns, noting that even in modern hospitals like UCLH, built less than 20 years ago, airflow dynamics were unpredictable. This Thailand Hospital News report underscores the importance of understanding these dynamics to ensure patient and staff safety.
 
Detailed Experimentation and Findings
The clinic under study comprised a large central waiting area divided into sections A and B, eight consulting rooms, and a nurses' station. Experiments were conducted during off-hours to ensure no staff or patients were present.
 
Researchers placed aerosol generators in specific rooms and used particle detectors in other areas to trace particle movement. In one experiment, they simulated particle spread from a consulting room to an adjacent room. Closing the door of the source room significantly reduced particle spread, and closing both the source and neighboring room doors reduced it by 97%. However, when doors were open and large PACs in the waiting room were activated, particle spread to the neighboring consulting room increased by 29%. Introducing small desktop PACs to both consulting rooms and the nurses' station slightly reduced particle spread but not below baseline levels.
 
Dr. Jacob Salmonsmith from UCL Mechanical Engineering explained, "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." He highlighted the complex interactions between various air currents, such as ventilation systems, door movements, and human activity, emphasizing the need for comprehensive consideration when implementing air cleaners.
 
Complex Airflow Patterns
In another experiment, with all consulting room doors open, researchers observed intricate patterns of particle spread. Notably, the highest concentrations of particles were detected in rooms farthest from the aerosol source, especially where a PAC was operational. For instance, particle levels in the room farthest from the source were 184% higher than average, while the room directly opposite the source had levels 68% below average. Additionally, there were 247% more particles in the waiting room section farthest from the consulting room with the aerosol source than in the section right next to it. The nurses' station also exhibited higher particle concentrations than any room on the same side of the clinic as the source room.
 
Professor Andrea Ducci from UCL Mechanical Engineering noted, "Our experiments demonstrated that high volumes of particles can be corralled into particular areas as a result of airflow dynamics. This obviously isn't ideal, particularly if that place is a key location, such as the nurses' station that staff members who're treating patients will likely visit often during their shift." He emphasized the importance of understanding these dynamics to identify simple interventions, such as better positioning of ventilation devices, to reduce particle spread and decrease infection risks in hospitals.
 
Implications and Future Directions
The study underscores the necessity for careful consideration of airflow dynamics when deploying ventilation systems and PACs in hospital settings. The unpredictable nature of aerosol movement highlights the potential risks of exacerbating viral spread if these systems are not appropriately configured. The authors suggest that governmental action should ensure that NHS standards for ventilation and infection control are fit for purpose, aligning with efforts to prevent future pandemics. They are currently developing an AI system to simulate entire clinic airflow and assess the efficacy of different devices in various positions, aiming to start testing within the next 18 months.
 
Conclusions
This research indicates that while ventilation systems and PACs are essential tools in mitigating airborne viral transmission in hospitals, their implementation requires meticulous planning. Unintended consequences, such as increased particle spread to certain areas, can arise from improper placement or usage. Therefore, it's crucial to consider the specific airflow dynamics of each hospital environment. Future strategies should involve comprehensive simulations and analyses to optimize the placement and operation of these systems, ensuring they effectively reduce infection risks without inadvertently promoting particle dispersion.
 
The study findings were published in the peer reviewed journal: Aerosol Science & Technology.
https://www.tandfonline.com/doi/full/10.1080/02786826.2024.2446587
 
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