Air pollution is acknowledged by the World Health Organisation as the greatest environmental threat to global health. Nine out of ten people breathe polluted air every day, and poor air quality leads to over 7 million people dying prematurely annually. In recent years, outdoor air quality has started to receive the much needed attention it requires, but indoor air quality has remained overlooked. This is alarming considering the fact that levels of indoor air pollutants are often 2 to 5 times higher than outdoor levels. We also tend to spend over 90% of our time indoors, and presumably this figure is currently closer to 100% for many as a result of lockdown restrictions.
Air quality in buildings has long been a cause for concern, but the COVID-19 pandemic has undoubtedly accentuated the need for healthier indoor air. There have been many studies confirming that air quality has a direct correlation with COVID-19, and there is mounting evidence to suggest that the virus is airborne.
Viruses can be transmitted via the air through either close contact transmission through large droplets (> 10 microns), or through airborne transmission through small particles (< 5 microns). These small virus particles may stay airborne for hours and can be transported long distances, carried by airflows in rooms orthe extraction air ducts of ventilation systems. ASHRAE have stated that transmission of COVID-19 ‘through the air is sufficiently likely that airborne exposure to the virus should be controlled’, through ‘changes to building operations, including the operation of heating, ventilating, and air-conditioning systems’. Furthermore, BESA have advised that clean air technologies and strategies should be adopted by every healthcare facility in the UK in the wake of COVID-19. It is clearly even more essential than ever for steps to be taken to improve the air quality inside buildings.
The ventilation industry will have a pivotal role to play in making buildings safe, particularly when we start to emerge from lockdown. Future buildings will need considerably improved ventilation systems to tackle cross-contamination and air distribution. To make current buildings safer, increasing ventilation is a vital step to reduce the risk of airborne transmission. The general advice is to supply as much outside air as reasonably possible, in order to increase the amount of fresh air supplied per person.
This can be achieved by keeping ventilation running for longer periods of time, or keeping it on constantly, but at a lower rate when people are absent. Ventilation is also enhanced by maintaining sufficient spacing between occupants. When employees return to their offices, it will be important that they remain spread out and are not confined in small areas for long periods of time, as this could lead to inadequate ventilation. Where possible, opening windows is another effective way of boosting air exchange rates. It is also advisable for decentralised systems such as fan coil units that use local recirculation to be turned off, to avoid resuspension of virus particles at room level. If it is not possible for these systems to be turned off, they must be cleaned regularly.
Installing air purification systems
Whilst ventilation systems are important in order to increase air supply, they do not typically clean or purify the air inside a building, and leave harmful substances and toxic pathogens in the air. Even the best HVAC system cannot completely prevent the transmission of COVID-19 by droplets or aerosols, meaning that localised air purification is crucial to maintaining a healthy environment. Unfortunately, many air purifiers are not particularly efficient. To be effective, they must have HEPA filter efficiency, as these filters can capture particles within the size range of COVID-19. The right type of air purification technology can be extremely effective in removing pathogens from the air, making it cleaner and healthier.
Air quality and COVID-19
Recent studies confirm the link between poor air quality and the infection and survival rates from COVID-19. A Harvard study led by Professor Francesca Dominici along with Doctoral student Xiao Wu and Assistant Professor Rachel Nethery showed the link between long-term exposure to PM2.5 and the mortality rate of COVID-19. Their research found that a one unit increase (1 ug/m3) in long-term average exposure to fine particulate matter was associated with a 15% increase in COVID-19 mortality rate on average.
Furthermore, a study by Yaron Ogen from the Martin Luther University of Halle-Wittenberg in Germany found that NO2 is also linked to higher COVID-19 death rates. Ogen looked at satellite data to map the distribution of NO2 across Europe in the months leading up to the pandemic, and charted the number of COVID-19 deaths from 66 regions in Spain, Italy, France and Germany. Results showed that out of the 4,443 fatality cases, 3,487 (78%) were in five regions located in north Italy and central Spain with the highest NO2 concentrations.
Transmission of viruses in buildings can also be limited by changing air temperatures and humidity levels. Research to date suggests that COVID-19 is fairly resistant to environmental changes and is only affected at a high relative humidity above 80% and a temperature above 30 degrees. However, low humidity can cause mucous membranes to dry out, which compromises our body’s natural defence to viruses.
The benefits of real-time indoor air quality monitoring in this scenario are limitless. By implementing sensors that monitor temperature, humidity, CO2, CO, NO2, O3, TVOCs and PM2.5, you can ensure that these parameters stay within optimal levels. Whilst COVID-19 is currently the most pressing concern, ongoing air quality monitoring can also prevent Sick Building Syndrome and optimise occupant wellbeing. Smart alerts can be set up to notify your Facility Team when environmental parameters deviate from their optimal zone, and remedial action can be taken via your Building Management System (BMS) where appropriate. For example, ventilation can be increased to improve your air quality and create a healthier environment for occupants.
It is evident that poor indoor air quality can no longer be ignored. It is vital for steps to be taken to make buildings safer for occupants, including improving ventilation, implementing air purification technology, and undertaking real-time monitoring of key parameters. Perhaps one positive outcome of this devastating pandemic will be to draw attention to one of the biggest ongoing health threats we face; poor indoor air quality.
With the current rules in place to tackle the spread of COVID-19, you are undoubtedly spending more time in your home than ever before. This means ...