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New REHVA guidelines focus on airborne COVID-19

The European Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA) has released an updated guide on how to operate HVAC and other building service systems to prevent the spread of COVID-19 in workplaces.

The revised document puts a greater emphasis on the potential for airborne transmission of COVID-19. Accordingly, it proposes an infection control hierarchy in which engineering controls such as ventilation systems are rated as more important than physical distancing and PPE.

“It is impossible to say whether aerosol-based transmission has a major or just a significant role,” the guidance document notes. “Transmission routes also depend on the location. In hospitals with an excellent 12 ACH ventilation rate, aerosol transmission is mostly eliminated, but in poorly ventilated spaces, it may be dominant.

“It is concluded that there is no evidence to support the concept that most respiratory infections are primarily associated with large droplet transmission and that small particle aerosols are the rule, rather than the exception, contrary to current guidelines.”

REHVA also notes, however, that there is currently no evidence of human infection with SARS-CoV-2 caused by infectious aerosols distributed through the ventilation system air ducts. It rates this risk as “very low”.

The document provides three main areas of guidance:

  • How to operate HVAC and other building services in existing buildings during an epidemic
  • How to conduct a risk assessment and assess the safety of different buildings and rooms
  • More far-reaching actions to further reduce the spread of viral diseases in future in buildings with improved ventilation systems.

There are 15 recommendations that REHVA says can be applied in existing buildings at a “relatively low cost” to reduce the number of cross-infections indoors.

“Regarding airflow rates, more ventilation is always better, but is not the only consideration,” says REHVA.

“Large spaces such as classrooms, which are ventilated according to current standards, tend to be reasonably safe, but small rooms occupied by a couple of persons show the highest probability of infection even if well ventilated. While there are many possibilities to improve ventilation solutions in [the] future, it is important to recognise that current technology and knowledge already allows the use of many rooms in buildings during a COVID-19 type of outbreak if ventilation meets existing standards and a risk assessment is conducted.”

The newest version of the guidance also focuses on how to reopen and safely use buildings after the lockdown, providing advice on specific components, buildings/space types, and suggesting mitigation measures.

To read the guidance document, click here.

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