UK schools have received more than 300,000 CO2 monitors as part of a government initiative to reduce COVID-19 spread in classrooms.

A collaboration between Imperial College London and the Universities of Cambridge and Surrey is supporting the rollout of portable monitors to UK schools as part of project CO-TRACE, which is funded by the Engineering and Physical Sciences Research Council (EPSRC). The researchers behind the collaboration have produced materials to help teachers use the monitors, which have been rolled out to schools nationwide.

The monitors empower teachers to strike a balance between good ventilation and warmth during winter. Dr Henry Burridge Department of Civil and Environmental Engineering

The level of carbon dioxide (CO₂) in a closed space is a good indicator of air quality and can signpost the need for ventilation. As the virus that causes COVID-19 is airborne, ensuring the air is properly refreshed using ventilation is crucial for reducing its spread.

The monitors rolled out to schools display levels of CO₂ and colour coding to indicate good, normal, or poor ventilation. Well ventilated spaces should have CO₂ levels consistently below 800 parts per million (ppm), with readings above 1500ppm indicating poor ventilation or over-crowding.

Co-investigator on the project Dr Henry Burridge, from Imperial’s Department of Civil and Environmental Engineering, said: “CO₂ monitors allow teachers to assess the ventilation in their classrooms for the first time. Monitoring air quality is especially important during colder months when ventilation is typically lower due to colder outdoor temperatures, causing COVID-19 and other airborne diseases like 'flu and the common cold to linger and spread more easily.”

The monitors mean teachers can see CO₂ levels change in real-time as windows are opened and air is refreshed, allowing them to balance ventilation and warmth. Teachers can also use the monitors to know when it is safe to close windows slightly, which could help them keep classrooms more comfortable. As well as being a good ‘proxy’ for ventilation, lower CO₂ levels have been linked to improved learning outcomes and better cogitative performance.

We are pleased that the government is taking evidence-based action to address air quality and COVID-19 spread in schools. Dr Henry Burridge Department of Civil and Environmental Engineering

The team behind the CO-TRACE project uses experimental modelling, numerical simulations, full-scale observations, and infection risk modelling to understand how the potential for COVID-19 spread changes with indoor air flows, ventilation levels, and the number of people in a space.

In 2021, the researchers used monitored CO₂ to indicate how much exhaled breath was present within classrooms, and their models found that seasonal variation in classroom ventilation levels could lead to airborne infection risks in winter being roughly double those in summer. This highlights that monitoring excess CO₂ could be of significant benefit in mitigating airborne infection risk.

The portability of the CO₂ monitors, supplied by the Department for Education (DfE), means schools can move them around to test different areas, starting with those they suspect may be poorly ventilated.

Dr Burridge added: “The monitors empower teachers to strike a balance between good ventilation and warmth during winter. We are pleased that the government is taking evidence-based action to address air quality and COVID-19 spread in schools.”

The monitors are accompanied by advice from the project which guides appropriate actions from teacher based on the CO₂ readings in classrooms. Recommendations include opening higher windows before lower ones, and closing windows slowly when ventilation is good.

Schools with areas that are consistently low in air quality despite ventilation should consider using air cleaners. For such schools, the the DfE is distributing between 7,000 and 8,000 air cleaning units.

When the project was announced in 2021, then-Education Secretary Gavin Williamson said: “Providing all schools with CO₂ monitors will help them make sure they have the right balance of measures in place, minimising any potential disruption to education and allowing them to focus on world class lessons and catch up for the children who need it. By keeping up simple measures such as ventilation and testing, young people can now enjoy more freedom at school and college.”

The project is funded by the EPSRC, part of UK Research and Innovation (UKRI).

Main image: Shutterstock

Image 1: Co-Schools