Recognising the need for good ventilation in buildings is not new. In the mid-19th century, Florence Nightingale alerted us to the benefits of fresh air in her book, ‘Notes on Nursing’, which stressed the importance of opening windows in hospitals to promote health as long as patients were kept warm.
Ventilation exists for two principal reasons – to provide comfort and to promote health. The factors that have the biggest influence over comfort and health are temperature and indoor air quality.
While temperature is important to the health, welfare and performance of building occupants, a growing recognition that airborne transmission is a critical route to COVID-19 infection has focused people’s minds on the importance of air quality.
Cath Noakes knows all about this. As professor of environmental engineering and deputy director of the Leeds Institute for Fluid Dynamics, she studies how air moves, and the infection risks associated with different ventilation systems.
Early in the pandemic, she was invited to join the government’s Scientific Advisory Group for Emergencies (SAGE) and asked to study the transmission routes for COVID-19.
In July las year she, together with many other scientists, urged governments around the world and the World Health Organisation to recognise that COVID-19 could be transmitted in tiny particles in the air.
Professor Noakes’ research highlights the importance of good ventilation as a way to stop the spread of infection in indoor environments. As she points out: “The environment has an influence on transmission [of pathogens] … ventilation matters.”
As a recent guest on Radio 4 programme ‘The Life Scientific’, she talked about her life and work. She explained that people can get infected with COVID-19 when they are very close to others and breathe in the different sizes of droplets [aerosols] that those people breathe out.
“But” she added, “when you are a bit further away you breathe in the very small particles only and they may, most of the time, be quite a small percentage of the particles. But, in a poorly ventilated space, they can build up and if you are there for a long period of time you may inhale enough of them to become infected.
“So, a well-ventilated space can dramatically reduce the risk of that long range transmission [from small particles] in an environment [by 50 to 70%].”
Why ventilation matters
There are two ways of dealing with a pandemic like COVID-19. One is to change our own personal behaviour and the other is to change the environment – the buildings – in which we live and work.
Looking to the future, we are going to need a combination of both. Says Professor Noakes: “One of the challenges with behaviour change is that it is actually quite hard to maintain, particularly things like wearing a face covering over a long period of time.
“Changing our environments is more sustainable and resilient and doesn’t rely so much on people’s behaviour.”
But creating a well-ventilated space isn’t easy. The airflows in buildings are complex, they are affected by the positions of windows, the weather outside, wind direction, where radiators are located, where people are and how much they walk around disturbing the air.
There are also pockets where the air isn’t moving so infectious diseases can accumulate in these stagnant areas. Dilution ventilation demands that the air is mixed well in a space.
There are various technological options available to achieve this. For example, it can be accomplished with mechanical ventilation or, if the air needs to be treated, with air conditioning. Conditioning the air can also include purification and that is where air ionisers can really make a difference.
The choices are varied and complex and that’s why it makes sense to consult an expert. Klima-Therm has a wealth of experience and knowledge about how to treat the air in buildings to get right the delicate balance between good ventilation and energy efficiency.
To talk to one of our skilled professionals, email here, or call +44 (0) 20 8971 4195.