Whilst buildings themselves cannot solve the COVID-19 pandemic, it cannot be denied that they will play a crucial role in minimising viral transmission.
In fact, a recent study suggested that enhancing indoor air quality (IAQ) could be as effective in reducing aerosol transmission of viruses as vaccinating 50-60% of the population1.
As occupiers tentatively emerge back into their places of work, landlords are challenged with optimising the operational performance of buildings to the greatest extent possible, in conjunction with the enactment of behavioural change, to minimise risk and give their tenants peace of mind.
With significant links to cognitive function and risk of disease, including cancer, historic efforts regarding indoor environmental quality have typically focused on carbon dioxide, volatile organic compounds (VOCs) and particulate matter (PM). However, modern threats have led to a broader focus, encompassing humidity, temperature, and lighting, all of which play an important role in determining viral survivability, immune system health and infection potential.
The complexity of aerosol transmission
As we know, the SARS-CoV-2 virus mainly spreads via respiratory droplets, released when a person coughs, sneezes or speaks. Such droplets cannot remain suspended in the air because of their weight, meaning that they quickly fall to the ground or a nearby surface. The duration for which a virus can survive on a surface depends on a multitude of factors, such as the surface type and the surrounding environment, including air temperature and humidity.
Smaller droplets, in the form of an aerosol, travel further than larger droplets and remain the air for longer. Research has not yet concluded whether COVID-19 is effectively transmitted this way but there is suggestive evidence. This is reflected by guidance from the World Health Organisation (WHO) on managing aerosol transmission, such as by implementing high-quality filtration, which could reduce infection risk by up to 47%2.
In dry air, droplets evaporate quickly, which means they fall more slowly, remain in the air for longer and travel further (for different reasons, a similar effect is noted at high levels of relative humidity). Consequently, research shows that at low levels of humidity — that which might commonly be found in UK offices during the winter — the infectivity of viruses is around 74%, compared with around 18% when optimised3.
Buildings are unique and approaches to managing indoor transmissions should be too
As guidance emerges from a variety of sources, often making blanket statements regarding the configuration of heating, ventilation, and air-conditioning (HVAC) systems, building operators should remain cautious as to not lose sight of the unique nature of buildings. For example, increasing outdoor ventilation might be a sound strategy for one building but could create poor temperature and humidity in another, leading to a reduction in immune system health and an overall increase in viral transmission risk.
How to build confidence in returning to the workplace safely
Such guidance is useful but should not be followed blindly. Instead, it is increasingly important to establish IAQ policies, asset-specific strategies, and feedback loops as to gauge the impact of operational changes, which could involve the installation of IAQ monitors or enhanced testing protocols. Whilst sensors capable of tracking viruses directly are still under development, there are now indices that can be leveraged for real-time monitoring of transmission risk, based on proxies and a combination of the factors mentioned herein, as well as certification frameworks that provide demonstrable strategies for viral transmission risk, encompassing IAQ enhancement.
Ultimately, building owners and operators will need to leverage a range of tools and strategies to give their tenants confidence in returning to the workplace safely. However, it is clear that an effective approach should be asset-specific and should encompass an increased focus on the monitoring and management of air quality, particularly regarding broader environmental factors that may have previously been considered peripheral.
- Smieszek, T., Lazzari, G., & Salathé, M. (2019). Assessing the Dynamics and Control of Droplet- and Aerosol-Transmitted Influenza Using an Indoor Positioning System. Scientific Reports, 9(1)
- Azimi, P., & Stephens, B. (2013). HVAC filtration for controlling infectious airborne disease transmission in indoor environments: Predicting risk reductions and operational costs. Building and Environment, 70, 150-160.
- Noti, J. D., Blachere, F. M., McMillen, C. M., Lindsley, W. G., Kashon, M. L., Slaughter, D. R., & Beezhold, D. H. (2013). High humidity leads to loss of infectious influenza virus from simulated coughs. PloS one, 8(2), e57485. https://doi.org/10.1371/journal.pone.0057485