SERVICE AND MAINTENANCE
The role of
ventilation in service and maintenance
This report from Swegon looks at the role ventilation plays when it comes to managing indoor environments.
I
n 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 a 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
26 May 2021
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.
Sustainability 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 better 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, engineers must work alongside the government to ensure improved, healthier and sustainable environments are kept on the agenda. We must continue to work towards solutions 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.
Scientists now believe that airborne aerosols are the most likely way to contract the disease. The World Health Organisation (WHO) took some time to recognise this threat, but by last autumn inhalation of aerosols was accepted as the main driving force behind the surging new wave of infections and this led to the increased emphasis on wearing face coverings. The role of mechanical ventilation is also
now better understood. Historically, the focus for indoor climate was on temperature control, which is of course important in terms of comfort, but the health and wellbeing role of ventilation is now more widely understood as a result of the pandemic. The higher the rate of ventilation, to give maximum dilution of contaminants, the better. The government’s SAGE advisory group has, therefore, called for a national strategy on building ventilation backed up by research from Cambridge University recommending that air change rates should be adequate to keep carbon dioxide levels below 800 parts per million as an indicator that all potentially harmful contaminants are under control. This may suggest that ‘all-air’ systems are the answer, but these will often be impractical or uneconomical because of the size of the plant and services necessary to deliver sufficient levels of cooling to the building. In such cases where secondary cooling systems will be required, there are choices; those that rely on a primary air supply to function
www.acr-news.com
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