See You later, CO2

As schools get ready to start 2022, in the middle of the current wave of the Omicron variant, again we hear how important education is and the call for disruptions to be minimised. Over the past 3 months the government has finally decided to do something about the role ventilation plays in the transmission of COVID by focusing on monitoring CO2 levels and filter-based air purification. According to government figures, £25m has been invested in procuring over 300,000 monitors (unit cost of around £80 inc delivery) of which 329,231 had been delivered by 26th November 2021. In addition, a further 7000 air purification units will be procured.

IoT Horizon and partners over the past 18 months have highlighted the role that ventilation plays, not just in terms of COVID transmission specifically but more importantly on the wellbeing and productivity within the workplace. We produced the ventilation continuum which highlights the effectiveness (or otherwise) of different modes of ventilation.    


We can also see how government advice is slowly moving along that continuum, from the natural ventilation posture from last year towards the HEPA Filtration of the air purifiers.

During 2021, IoT Horizon ran a number of pilot schemes using our in-house designed and produced MPWR:Sense environmental sensor. This included monitoring the air quality, not just CO2 , in a number of workplaces including classrooms. In this blog, we discuss some of the findings and experiences from these pilots, and also highlight the overall benefits of strategically tackling air quality, rather than adopting a short-term tactical approach for the educational sector. This article also shows the relative ease of adoption of a strategic approach which applies not just to education but in other workspaces and public areas.

So why the focus on monitoring CO2? There are two reasons. Firstly, the level of CO2 is determined by the effectiveness of the ventilation, so a high CO2 level is indicative of poor ventilation. We also know that in poorly ventilated spaces, the viral density of COVID is higher, which increases the risk of transmission.  However, the second reason for the attention to CO2 and this is particularly relevant given how much classroom time has been missed due to COVID, is productivity and cognitive processing which is demonstrably diminished in spaces with high CO2 levels. This means if we want to catch up on the lost education time, it is better if the environment has lower CO2 levels. In simple terms, if we can manage CO2 levels in our classrooms and other workspaces, we can reduce the risk of COVID transmission and increase productivity to help catch up on missed lessons.

The Department for Education has recommended the following limits for CO2 . Under 800ppm is recommended and a desirable level. Between 800 & 1500ppm is considered “Amber” whilst above 1500ppm can adversely affect concentration. Also being measured are the ambient temperature and humidity. Given that COVID persists longer in cooler , drier conditions, then a warmer temperature, 18-22 Celsius with humidity in the range of 50% to 60% further reduces the risk of transmission.

The key points which are different this year compared to last year are the realisation that:

  • Ventilation is an important factor in minimising the risk of COVID-19 transmission, however, organisations can struggle to manage ventilation effectively.
  • Since CO2 is in exhaled breath, it can be an effective proxy for occupancy and/or ventilation but it is not a direct proxy for infection risk.
  • CO2 monitoring can be a cost-effective way of helping to identify workspaces with high occupancy and/or poor ventilation and pro-actively managing ventilation in that workspace.

Introducing CO2 monitoring is technically straightforward to do, however it is better to do this as a part of a strategic approach to air quality in general rather than a quick fix, tactical approach. Sadly, the approach recommended to the education sector is very tactical with the use of portable CO2 monitors that also measure temperature and humidity. Whilst we understand the attraction of doing something, the key to success in this case is not just being able to measure the CO2 levels at a point in time but manage the CO2 level and change the behaviours of the occupants in the room. We found when occupants were reminded to open windows once thresholds were triggered, the level of CO2 could be reduced – highlighted in the yellow box below – breaking the link between high occupancy and high CO2 levels.

However, when left to their own initiative, behaviours didn’t change and the link between high occupancy and high CO2 levels restored. Just because the monitor moves room, it means that the behaviours are likely to revert back to the previous situation and any benefit is only temporary.  

There are a couple of other issues presented by the current approach. Unless readings are manually recorded, it is not possible to get an idea of the trends and generate actionable insights into the environmental management of the room. Secondly, what happens when the monitor is moved or switched off? From our pilots we have been able to identify areas of improvement –such as heating the classrooms when they are not occupied, for example of an evening, weekend and even half term.  The current approach becomes counter productive as attention is drawn to the observing of the monitor readings to see if it is going up or down rather than focusing on the lesson. Although CO2 , Temperature and Humidity are measured, there are other factors that impact the classroom environment which are not measured. Finally, there has been some anecdotal evidence from school caretakers about the battery life of the monitors and I suspect the cost of such high battery replacement has not been factored in. Whereas, the battery life in the IoT Horizon MPWR:Sense is measured in months. But the monitors supplied are clearly not designed for continuous monitoring.

Our Experience

We have installed Air Quality Sensors in various sized and subject matter classrooms, and we have found different subject matters produce different CO levels. So, for example Geography lessons seem to produce higher CO2 levels more frequently than English.

The use of a dashboard, like IoT Horizon’s platform helps not only deal with alerts but also generates insights, for example, high formaldehyde readings due to recent redecoration could cause respiratory problems. Therefore, ventilation should be increased until the formaldehyde reading is at a more reasonable level.

Although CO2 monitoring is relatively simple to do and provides a good balance between ventilation, thermal comfort, and energy use, effective CO2 monitoring requires education. As demonstrated earlier, users need to understand what the monitor levels means and what they need do to in the event of an alarm. It is not a one-off exercise, but users need to be reminded frequently to enable the monitors to be used effectively to sustain better ventilation and occupancy behaviours. CO2 monitoring is not a direct mitigation; it is a means to guide additional actions to manage ventilation.

There are other equally airborne harmful substances such as dust, formaldehyde & other Volatile Organic Compounds (VOCs). These should also be monitored to ensure the air quality is optimal for the purpose of the workspace and classroom.

The number of occupants, noise levels, light, temperature, humidity and even swings in air pressure are other factors which can negatively impact the classroom environment and reduce productivity.

So, whilst CO2 monitoring is a start, it is only a start. By looking at the wider picture of air quality, we can get a long term, much more beneficial solution in place.

Finally, there is a group that are often overlooked in the CO2 and air quality conversations. The focus is always on those who are in the room for one or two times per week. However, there is another group of stakeholders who are in the room for every lesson – the teachers and classroom assistants – for whom the classroom is their workplace. They are exposed day in and day out to the potentially harmful air quality in the classroom. Just like any other employee in the workplace, their employer needs to fulfil their workplace obligations to provide a safe and healthy environment. Our initial studies have exposed that this is not always the case. Not only are teachers often overlooked, but it is also perhaps the most critical room in the school in terms of preventing any spread both in classrooms and the staff room. Here teachers and assistants who have been exposed by a pupil interaction can spread to other members of staff.

When we were first engaged in education at the start of the pandemic, one Headteacher gave the schools perspective of the situation. From their point of view if half the class is absent due to isolation or contracting COVID, the classroom & school can still function. From schools opening today, one secondary school Headteacher reported that on “today’s return of secondary schools in England, he and 26 of his staff had tested positive for the virus.” If the teacher is absent, (as the recent attempts to attract retired teachers back illustrates) this is a completely different matter. It is not just the direct cost of providing a substitute, but also indirect costs such as the whole class missing their lessons and falling behind. This is why teachers and teaching staff need to be considered too and not just focusing on the pupils.

Everyone agrees with the problem statement: our children’s education should not suffer further as a result of COVID, in particular, the impact of the current variant should not further adversely impact their education. However, just monitoring CO2 is only a short-term tactical response, better than doing nothing but much more could be done. Instead of focusing on one, easy, simple aspect of air quality – CO2 – a more productive, and longer term, approach would be to look at tackling air quality in general. IoT Horizon with its MPWR:Sense environmental sensor and our platform dashboard can capitalise on this tactical opportunity and turn it into a longer term win, where pupils get a safe, productive environment to learn and teachers get a safe, productive environment to teach. Schools can offer a better, managed environment and optimise their operating costs, which releases resource to providing a better, irrespective of the COVID variant or other environmental threat.


Leave a Comment

Your email address will not be published. Required fields are marked *