University researchers have discovered overuse of ventilation and air cleaners, which aim prevent the spread of viral infections, can achieve the opposite.
University College London (UCL) experts examined how built-in mechanical ventilation and portable air cleaners (PACs) affect the spread of airborne particles such as those from respiratory infections.
The team tracked particle movement in an outpatient clinic at UCL Hospital and paid close attention to the waiting room, eight consulting rooms, a nurse’s station and a storage room. Experts also tended to conduct their experiment late or night or on the weekend to make sure fewer people were present.
The findings revealed that while built-in ventilation and PACs can reduce particle spread in some cases, in other experiments PACs actually increased aerosol spread by up to 29% between neighbouring rooms, while built-in ventilation increased aerosol migration across the clinic by more than five times, compared to no ventilation.
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.’
Professor Andrea Ducci, an author of the study from UCL Mechanical Engineering, said: ‘Our experiments demonstrated that high volume 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.
‘The good news is that we’re rapidly expanding our knowledge of this phenomenon. The project that we are currently working on aims to simulate the entire airflow within a clinic and assess the efficacy of different devices positioned in different locations. This will allow us to identify relatively simple interventions, such as better positioning of ventilation devices to reduce the spread of particles, thus decreasing the risk of picking up an infection in hospital.’
The full research can be read here
In related news:
Brutality against UK women and girls is spiralling, watchdog reveals