Office HVAC

Ventilation beats open windows

Ventilation systems can halve the risk of spreading airborne diseases like COVID-19 in offices compared to opening windows, according to new research from S&P Ventilation Systems

With everyone wearing a mask, there would be four infected workers with natural ventilation and two for mechanical ventilation, according to the research. The Scientific Advisory Group for Emergencies (SAGE) says building ventilation should be “integral to the COVID risk mitigation strategy for all multi-occupant public buildings” with growing numbers of experts calling for urgent action over better indoor ventilation.

Managing director of S&P UK, Alex Finch, (pictured right) said: “Our research provides much-needed evidence for businesses to take action with the office floodgates expected to open on 19 July ‘Freedom Day’ as part of the country’s new flexible working regime.

“There’s plenty of general advice on ventilation but many firms are crying out for clear-cut guidance. The failure to distinguish between mechanical or natural ventilation as part of this debate is also not surprising as it’s a complex and new challenge.

“But our evidence is clear: mechanised ventilation systems are twice as effective as natural ventilation at preventing the spread of airborne diseases in indoor workplaces like offices.


he company has released the findings of a detailed study carried out by its European R&D centre to shed light on whether mechanical or natural ventilation should be used to improve air quality and curb the risk of contracting airborne diseases indoors. COVID-19 is spread via infectious aerosols which can stay airborne for long periods, particularly in poorly ventilated areas.

However, the study by S&P UK found mechanical ventilation systems can cut by half the risk of aerosol

transmission compared to natural ventilation – opening windows and doors which is often impractical due to street noise, pollution and cold air during the winter. There are long-held concerns that most offices only recirculate existing air with air conditioning units, rather than pumping in fresh air using mechanical ventilation systems – affecting indoor air quality.

It comes amid reports that the work-from-home guidance will be lifted on 19 July in line with the Government’s roadmap – prompting an expected mass return to the office this summer.

The scientific modelling and analysis by S&P researchers considered 40 workers in an open plan office with a total area of 260 metres squared and a total volume of 780 metres cubed.

In the scenario of an infected employee working Monday to Thursday, with no mask wearing as per the 19 July roadmap, there would be 13 people infected if the only ventilation is open windows. However, with an indoor ventilation system in place, this figure drops to eight.

“We advise business owners and landlords to consider investing in ventilation systems to help safeguard staff and visitors whilst also taking measures to improve indoor air quality.”

The British Medical Association (BMA) said the Government has clearly conveyed the “hands, face, space” message, but more needs to be done to guard against airborne transmission of COVID-19. Pubs, bars and restaurants should be given ventilation guidance as they welcome the public indoors again, the BMA added.

14 August 2021


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