Class monitors: assessing school indoor air quality

A project assessing the risk of airborne Covid-19 transmission in schools has released four videos about the importance of monitoring air quality. The project’s co-investigator, Dr Henry Burridge, explains

The Co-Trace project, launched in February 2021, brings together researchers from the universities of Cambridge, Surrey and Imperial College London to assess the risk of airborne Covid-19 transmission in schools, and evaluate the effectiveness of mitigation measures.

Alongside principal investigator Paul Linden, of the University of Cambridge, co-investigators Henry Burridge, Christopher Pain (both of Imperial College London) and Prashant Kumar (University of Surrey) have been modelling and assessing data from air quality monitors in schools to support ventilation guidance.

As part of the project, the team has produced four videos to assist classroom staff  in using CO2 monitors provided by the Department for Education (DfE). Here, Dr Burridge, senior lecturer in fluid mechanics at Imperial College, explains the aims of the project.

Why was Co-Trace set up and what are its aims?

Through the Royal Society’s Rapid Assistance in Modelling the Pandemic initiative, we identified that schools were going to be a potential source of Covid transmission. We were aware that ventilation was an important mitigation measure in UK schools, which typically have no mechanical ventilation provision.

The Co-Trace research project has been focusing on detailed studies of schools, where we have been placing air-quality monitors and modelling the implications.

I am also joint principal investigator on the DfE’s pilot project investigating the changes in ventilation of schools when CO2 monitoring is carried out. I felt it was excellent that the government was rolling out monitors to help classroom staff. However, I became aware of the need to help teachers understand why they were being sent these monitors, and how to use them and interpret the information, so we felt we should make the videos and materials. 

Phase one of Co-Trace will end in August, and we have secured funding for an extension project, School Air Quality Monitoring for Health and Education. This will involve sending out monitors to a few thousand schools to record data for analysis.

Can we reduce the risk of children becoming infected with Covid-19?

Primary school children are challenging, because they interact with each other closely, and are in close contact for long periods. One of the things we can do to try to mitigate the spread of Covid through the air is to ventilate classrooms appropriately, or encourage outdoor play where possible. In terms of ventilating a classroom, if the children are sitting still, they will not be learning effectively if they are freezing cold. Last winter, the advice was open all of the windows all of the time, but these monitors enable us to say, ‘use your monitors to strike the right balance between opening windows and keeping a comfortable environment’.

Should other measures be considered, such as air cleaning devices?

If classrooms for which the ventilation architecture (windows and doors), heating provision and room usage mean the space cannot be ventilated adequately, school leaders need to consider all options. Some long-term solutions can be expensive and take a while to put in place. For example, should contractors need to implement a solution over, say, the summer holidays, air cleaners are something to consider as a short-term solution. An online marketplace of suitable devices is at this Department of Education site

Can this guidance be applied to other indoor environments?

Yes. In my university department, for example, we have established CO2 monitoring in all teaching spaces; we use the data to support our estates team in checking and maintaining the mechanical ventilation provision. We also provide CO2 monitors in naturally ventilated teaching spaces, so lecturers can manage the ventilation.

If I was responsible for office space, I would undertake CO2 monitoring to check the balance between occupancy and ventilation. It’s relatively cheap to do, and either gives peace of mind, or can quickly identify issues that are sometimes relatively easily addressed.

Is there an opportunity for more education on indoor air quality?

Long term, the way to make sustainable changes to our indoor environments and ensure everyone’s wellbeing is improved, without costing too much in energy, is through good education. You need occupants to understand why they should care about the air quality they’re exposed to and how they can play a role in managing that exposure.

Find out more, and watch the videos, at