Comment & Analysis
At the beginning of the pandemic, there was an important question to resolve: is coronavirus ‘airborne’? If it was, then this meant that the virus could transmit through the air from person to person, even over long distances, in indoor environments. We now know the answer is yes.
In the 19th century diseases such as cholera and typhoid taught us the importance of water quality, coronavirus in the 21st century should provide that same realisation on the importance of air quality. Ideally, all indoor environments where people congregate should be fitted with modern, efficient ventilation systems that flush out potentially contaminated air and replace it with fresh, clean air continually. This would prevent the build-up of virus-containing aerosols and reduce the likelihood of transmission of COVID-19 and other diseases such as influenza.
However, modern effective ventilation systems are expensive and in older buildings can be difficult to install. Last winter countless schools, those attended by my children included, kept their windows open, even as temperatures plunged – an unsatisfactory, unsustainable, and costly solution.
When proper ventilation is not an easy option, a quick to implement and relatively cheap alternative can be air cleaners. These can be mobile units that are easily installed in, for example, schools, hospitals, or offices and provide a good level of protection from virus transmission. Experts from the Institution of Mechanical Engineers have already worked with the NHS to agree a standard required to roll out UVC (ultraviolet) based air sanitiser use in hospitals. It is important now that hospital administrators are aware of tried and tested solutions as they continue to navigate through this crisis, and as government advice and legal requirements on ventilation continue to evolve. IMechE members are also involved in several studies to evaluate air cleaning technologies in schools including a demonstration project at St Teresa’s School in Morden, and an evaluation trial at 30 primary schools in Bradford.
Increasing energy costs have put a sharper focus still on the need to roll out safe, affordable and sustainable solutions for our air quality in busy public spaces. A range of technologies exist but experts at the Institution of Mechanical Engineers have assessed that both filter-based and UVC air cleaners have a high potential to reduce virus transmission and energy costs. While filter units are increasingly common there is less knowledge about UVC devices. The principle that UVC can kill viruses has been understood for 175 years, and household appliances such as indoor fish tanks already use this technology to purify water. The technology works by using fans to pass air close to safely enclosed UVC lamps where the light damages any microorganisms carried by the air and renders them harmless. The introduction of air recirculation with UVC and a modest contribution of outside air requires much less energy option than ventilating at a high rate. Compared to other solutions using heat recovery, the equivalent UVC recirculation devices will only require around one tenth the energy. If we reduce window openings in cold weather, use of air cleaning devices can actually reduce the energy demand and accompanying carbon footprint while at the same time providing improved air quality and reduction in infection risks.
Two recent reports by the National Engineering Policy Centre (Infection Resilient Environments) have put forward proposals to make indoor environments safer in the coming years. These include quantitative evidence that the health benefits of improved ventilation are highly likely to outweigh the costs in a wide range of community and commercial buildings. It is important to remember that COVID-19 has not gone away and there will be other pandemics in the future. The reports highlight the fact that doing nothing will cost society more in the long term.
The Institution of Mechanical Engineers propose that we begin to address indoor air quality with the same degree of seriousness as society regarded clean water in the battle against cholera. If we are to safeguard people who have to gather in hospitals, schools, and public buildings then we need to make the air as safe as possible and we need to make sure that we do this in a cost-effective manner. Engineering solutions exist to do this, but we need decision makers to be aware of the best options to make buildings infection resilient. This will both make our buildings safer and allow us to reap the wider benefits of improved indoor air quality.
This article was first published by Health Service Journal