October 25, 2021
The model – developed by researchers at Imperial College London, the University of Cambridge and University of Leeds, and jointly funded by the PROTECT COVID-19 National Core Study and UK Research and Innovation – uses monitored CO2 and occupancy data to predict how many workers are likely to be infected by an asymptomatic but infectious colleague.
High indoor CO2 levels are related to lower ventilation rates and high occupancy, so monitoring them can provide an important red flag to building managers to identify areas of inadequate ventilation. This can help assess the risk of airborne transmission of the COVID-19 virus. Achievable interventions can then be made, for instance, to improve ventilation or change worker attendance patterns to reduce occupancy.
While applications of the infection model so far have demonstrated that most workers in well ventilated open plan offices are unlikely to infect each other via airborne particles, the risk becomes greater if the space is poorly ventilated or if the workers are involved in activities which require more speaking. For instance, the model predicts each infected person could infect two to four others in an adequately ventilated but noisy call centre. Risks are also likely to increase if the infected individual is a ‘super spreader’.
Dr Henry Burridge, Senior Lecturer in Fluid Mechanics at Imperial College London and lead author of the paper, said: “In shared spaces such as offices and classrooms, exposure to infectious airborne matter builds up over time, during which room occupancy may vary. By using carbon dioxide levels as a proxy for exhaled breath, our new model can assess the variable exposure risk as people come and go.
“Our work emphasises the importance of good ventilation in workplaces and in schools. The model demonstrates that by managing the ventilation and occupancy levels of shared spaces we can manage the risk of airborne infection by a virus such as that which causes COVID-19.”
Professor Andrew Curran, Chief Scientific Adviser at the Health and Safety Executive and lead for the PROTECT study, added: “This important research demonstrates that, while the airborne transmission route can be a significant contributor to COVID-19 infection risk in places such as offices and schools, there are achievable steps that can be taken to reduce this risk and help facilitate a safe return. Ensuring adequate ventilation is a key element, and the appropriate use of tools such as CO2 monitoring can give building managers a much better understanding of their own ventilation systems and how they are performing for each activity undertaken in the space.
“However, the airborne route is just one of three known routes of transmission of the COVID-19 virus. Close-range person-to-person and surface transmission risks must also be assessed, and relevant measures applied to control all routes of exposure for all activities where risk is identified. For most businesses, a COVID-19 control strategy will involve a blended combination of measures identified through a risk assessment – there is no silver bullet.”
Professor Charlotte Deane, UKRI Director for the COVID-19 Response and Deputy Executive Chair of the Engineering and Physical Sciences Research Council, said: “A key challenge throughout the pandemic has been to understand how this novel virus is transmitted and to develop measures which could be implemented to curb the spread of infection. This study highlights that research and innovation supported by UKRI and the National Core Studies programme is continuing to evolve our understanding of the virus and helping us to develop knowledge which will be key to the global post-pandemic recovery.”
The full paper can be found here.
This is valid as of 25th October 2021.
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