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The more we learn about Covid-19, the more we hear about the role of ventilation or 'fresh air' in reducing transmission. However, ventilation isn't just for preventing virus transmission today. Good ventilation will bring many other health, wellbeing and productivity benefits to occupants in the long run...
Without a doubt, this pandemic had our leaders facing new challenges, and making tough decisions. By having to consider the country’s economic situation alongside both the mental and physical health of our population, our government had the unenviable and possibly unmeasurable task of attempting to reduce the spread of coronavirus with a variety of lockdown measures.
In the world of building services engineering, we have been trying to find a balance between the potential risk from ventilation systems and the many benefits they provide to building occupants. While there are still lots of things we don’t know about Covid-19, there are things we do now know that are slowly making that task easier.
For example, we now know the virus is airborne and capable of remaining active in the air for several hours. Therefore, attempting to dilute concentrations of the virus-bearing particles seems like sensible step, and the advice to operate mechanical ventilation systems at maximum ‘fresh’ air mode has not changed since the start of the first lockdown. Facilities managers also may have been advised to turn off rotary heat exchangers, however this advice has now changed.
This improved understanding will also help us support the government’s SAGE advisory group, which has called for ventilation to be “integral to the Covid-19 risk mitigation strategy for all multi-occupational buildings.” That advice was supported by a new study from Cambridge University, which showed how displacement ventilation could cut indoor transmission rates by introducing cooled air at lower levels that removes particles above head height as it warms and rises.
The Cambridge researchers also used CO2 concentrations as an indicator of air change rates and, therefore, the potential for airborne contamination. They suggested that CO2 concentrations above 700 parts per million (PPM) would indicate that the air was not being refreshed adequately to dilute the concentration of the virus in the air.
Although the current advice to schools and other public buildings is to keep their windows open as much as possible, this will rarely provide the air change rates needed. It is totally weather and temperature dependent and will, almost inevitably, mean some parts of a room are not ventilated at all – not to mention the risk of introducing external pollutants and noise.
We must also consider sustainability when it comes to our ventilation solutions. By choosing parts that are easily integrated into systems, we are able to ensure our ventilation systems offer more economic value over the years. On top of this, increasing thermal comfort helps improve the productivity of building occupants, and good indoor environmental quality is able to consistently reduce energy usage.
Whilst now is a good time than any to upgrade components of your ventilation system, good ventilation methods aren’t just for the Covid-19 pandemic. We must ensure we are continuing with good practices concerning ventilation and taking on board advice from industry experts as part of a longer term solution.
Together, we will work alongside our colleagues in engineering, government and society to ensure improved, healthier and sustainable environments are kept on the agenda. We must continue to find ventilation solutions for today that that are realistic and work in practise, without making rash decisions that may jeopardise people’s health and wellbeing, and have a negative impact on the environment in the long term.
