In this article, we explain how schools can use the CO2 monitors supplied by the DfE to effectively help identify areas with poor ventilation.

Read on for more detail!        

Here's what's covered in this article:

  • The DfE’s CO2 monitor programme
  • Deliveries and queries
  • Where to use CO2 monitors
  • Monitor placement
  • Monitor readings

Next steps

The DfE’s CO2 monitor programme


From the beginning of September 2021, CO2 monitors are being provided to all state-funded schools to reduce the transmission of coronavirus (COVID-19). Improving general air flow can help to create a safer environment for staff, pupils and visitors.

The monitors, which will be distributed over the Autumn 2021/2022 term, will enable staff to quickly identify areas with poor ventilation and provide reassurance that any current ventilation measures are working. The monitors can also assist staff to monitor more efficient ventilation alongside thermal comfort.

The monitors are to be used alongside current enhanced ventilation measures, which include keeping external classroom windows open and using mechanical ventilation systems.


Deliveries and queries


The DfE is providing non-dispersive infrared (NDIF) monitors to eligible schools; however, there are many types of monitors available. The monitors will come with either batteries or USB power cables and AC adapters. Schools will receive roughly one monitor for every two teaching rooms.

The monitors will be delivered by one of two suppliers: Rexel or CEF (Flamefast). If schools have any issues regarding the delivery or quality of their monitors, they should contact the supplier directly. For any further queries about the monitors, schools can call the DfE’s coronavirus helpline on 0800 046 8687.


Where to use CO2 monitors


CO2 monitors are best suited to spaces which are densely occupied for one hour or more. In schools, this includes, but is not limited to:

  • Teaching spaces – including lecture classrooms and practical teaching spaces
  • Indoor play spaces
  • Staff rooms
  • Large offices with multiple occupants
  • Meeting rooms
  • Group or breakout rooms

It is not recommended for CO2 monitors to be used in areas that are unlikely to provide reliable readings. These areas would include the following:

  • Large, open internal spaces
  • Spaces with high ceilings such as sports halls
  • Spaces that are densely occupied for shorter periods of time, such as corridors or lobbies
  • Areas with low occupancy density, including kitchens and toilets, or offices with only one or two occupants


Monitor placement



When deciding where to place the CO2 monitors, schools should initially prioritise spaces that constantly feel stuffy or have an unpleasant smell, as these are likely to have poor ventilation. Prioritising monitors for these spaces can help schools to effectively take action and improve their air quality.

CO2 monitors should be placed:

  • At head height when individuals are seated.
  • Away from ventilation outlets, such as grilles or windows.
  • At least 0.5 metres away from occupants – placing the monitors closer than this could result in inaccurate readings.



Schools can rotate monitors around the building to identify the ventilation needs across the whole school. Rooms should be monitored for one full day before moving the monitors to a different location. Schools should prioritise poorly ventilated rooms initially, as set out above, and once improved measurements are recorded, move the monitors to the rooms that are used the most or have the highest occupation density. If placed in a new room, the monitor may need to refresh a few times before settling on a new reading.

If the monitor readings show that rooms are consistently well ventilated, there is no need to continue keeping them on the rota for monitoring CO2 levels.

Depending on the model, the monitors will refresh and show a new reading any time from every few seconds to every 10 minutes.


Monitor readings


Staff may wish to check the measure shown on screen mid-way through and at the end of classes or ask someone in the class to do so. There should be no need to interrupt a lesson to take a reading. Regular readings should also be taken for monitors placed in areas such as staff rooms and offices.

If the monitor records a consistent value under 800ppm (parts per million), it does not require any action and implies that the space is particularly well ventilated. A consistent value of over 800ppm should be seen as an early indicator to improve ventilation in the area.

A consistent value of 1500ppm in an occupied space is an indicator of poor ventilation. This will also be indicated by a red light on the CO2 monitor supplied by the DfE. Schools should take action to improve ventilation where CO2 readings are consistently higher than 1500ppm, although there is no need to stop utilising the area.


A few good practice tips:

  • Continue with basic preventative measures such as regular handwashing.
  • Wait for five minutes to allow a reading to settle before taking any required action.


Next Steps


DfE (2021) ‘How to use CO2 monitors in education and childcare settings’

DfE (2021) ‘Schools COVID-19 operational guidance’

DfE (2021) ‘All schools to receive carbon dioxide monitors’