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Something in the air...

David Cook, technical product manager at Vent-Axia, explains what can be done to help ensure businesses and schools have good ventilation by evaluating existing ventilation and improving or upgrading it as necessary

Technical product manager at Vent-Axia Dave Cook

Public Health England has now confirmed airborne transmission of COVID-19. With cases of coronavirus rising, it is vital to use ventilation to help mitigate virus transmission in buildings. So, what do HVAC contractors need to do?

As temperatures fall, we’re all going to be spending more time indoors and with virus numbers rising this is a concern. In Public Health England’s guidance ‘COVID-19: epidemiology, virology and clinical features’ it acknowledges that airborne transmission can occur in ‘poorly ventilated’ spaces. With the return to schools and some work places, it’s essential existing ventilation is evaluated and then improved if needed to achieve sufficient ventilation. Ventilation is vital since it helps reduce the potential concentration of the virus in the air. The more air supply in the space the more the viral material is diluted.

There are over two million non-domestic buildings in the UK all with individual ventilation requirements and systems. Some buildings use windows for ventilation, others are designed with whole building mechanical ventilation systems, while some are fitted with air conditioning systems that only recirculate the internal air. With so many variables it is essential for businesses and schools to have ventilation guidance that allows employees to go to work where necessary and for pupils to attend school. Employers and headteachers need to reopen confidently, assured they have helped mitigate the risk of COVID-19 through evaluation of their ventilation ensuring the systems they’re responsible for are up to the job.


Fortunately, the Chartered Institution of Building Service Engineers (CIBSE) published the ‘CIBSE COVID-19 Ventilation Guidance’ in April giving detailed guidelines for building managers/operators to minimise the risks of airborne transmission of COVID 19. Within the guidance CIBSE’s overarching advice is to increase the air supply and exhaust ventilation, supplying as much outside air as is reasonably possible to dilute and remove the virus as much as possible.

More detailed advice includes: extending the operation times of supply and extract mechanical ventilation systems; starting ventilation at nominal speed at least two hours before the building usage time and switching to lower speed two hours after the building usage time; in demand-controlled ventilation systems lowering the CO2 setpoint to 400ppm to maintain operation; and to keep ventilation on 24/7 with lower ventilation rates when people are absent.

Meanwhile, The Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA) ‘REHVA COVID-19 Guidance Document’ similarly recognises the vital importance of ventilation when it comes to mitigating COVID-19. It cites ventilation as the principal engineering control to help control infection, thus giving further weight to the vital role ventilation plays. The guidance advises how to operate HVAC and other building service systems to prevent the spread of the COVID-19 and states that new evidence on airborne transmission “..has made ventilation measures the most important engineering controls in the infection control.” It adds that although physical distancing is important to avoid close contact “the risk of aerosol concentration and cross infection from 1.5m onward from an infected person can be reduced with adequate ventilation and effective distribution solutions.”

Existing systems

So, with ventilation central to creating a safer indoor environment, what are the options for HVAC contractors to consider to improve ventilation and indoor air quality? The first step is to evaluate current ventilation systems and where possible increase airflow from existing systems to meet the necessary air changes an hour. This will be above the 10l/s of airflow set out in Building Regulations Part F. The number of air changes will vary depending on the application. It is also important to switch ventilation to full fresh air mode where possible rather than recirculating air and adding fresh air where there is only air conditioning.

If extract fans are installed, they should be checked to make sure they are in working order. If not, they should be repaired or replaced. Spare parts are available so existing extract or ventilation systems can be fixed. Where clients are keen to add extra airflow easily and quickly rather than upgrading a whole building system, HVAC contractors can add commercial extract fans such as Vent-Axia’s T-Series which offers high performance ventilation with low running costs, through a simple wall or window mounted system that can be set up to either supply or extract.


Alternatively, if a current ventilation system needs upgrading, demand ventilation is a good solution. Demand Energy Recovery Ventilation (D-ERV) systems have sophisticated controls and sensors that can be used to easily adapt the system to the new COVID-19 requirements, providing ventilation appropriate to occupant needs. The sensors hand-inhand with the demand ventilation are very helpful in the fight against COVID-19 since a CO2 sensor acts an easy-to-measure proxy to ensure there are sufficient air changes an hour to dilute the virus in the air, without over ventilating when not required. Meanwhile, when it comes to specification, any new system being installed should allow added capacity for airflow to meet potential future pandemics.

For instance, Vent-Axia’s Sentinel Totus² D-ERV offers an effective solution to ensure good ventilation, with a range of sensors, such as CO2 and PIR occupancy detection which are employed to determine the room’s air quality, adjusting the ventilation requirements automatically and managing the system’s ventilation rates accordingly.

With ventilation repeatedly cited and advocated by research, industry bodies and Government as a way to mitigate transmission of COVID-19 indoors, now is the time for building and facilities managers to ensure there is enough airflow to dilute the virus in the air and improve indoor air quality. Evaluating current ventilation is therefore vital and then increasing airflow as much as possible to dilute the virus and so mitigate transmission to help keep everyone safe. 

24 November 2020


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