Can CO2 help with indoor COVID transmissions?

There are 3 types of COVID transmissions: Fomites (wash hands, surface cleaning), Droplets/Close-Contact Transmission (social distancing, hand washing) and Long-Range Transmission (ventilation).


Ventilation is the new buzzword and is the current strategy for controlling the spread of COVID-19 indoors. As more businesses open their indoor spaces and control of crowds are removed, it is important we understand the role ventilation and fresh air plays.


There will be a greater risk of viral transmissions when individuals are in the same room/space together for an extended period of time with low ventilation rates.


So how can we be sure we are safe?


CO2 monitoring can be a cost-effective way to identify spaces with high occupancy and/or poor ventilation, and for actively managing ventilation in a space. Professor Catherine Noakes, who specialises in airborne infections, warns that ‘the numbers are not exact and don’t tell you actual risk from the virus, but they are useful in helping you to improve general ventilation’.


If your room measures CO2 levels of 800ppm (parts per million), then your ventilation is probably good. However, if CO2 levels regularly rise above 1500ppm then you need to open the windows/doors to release the stale air and let in fresh air.


And what steps can we take?


We believe all homes and businesses should have an air quality monitor as it is essential to know the air you breathe.


  • In the workplace The law says employers must make sure there’s an adequate supply of fresh air (ventilation) in enclosed areas of a workplace. This has not changed during the pandemic. Your facilities manager should be able to tell you the ventilation strategy and if they are monitoring CO2 levels (see further reading below). Bringing in your own plug-in or portable Air Quality Monitor can give you peace of mind that you are working in a safe environment.

  • Shops, clinics, gyms, hospitality If doors and windows are closed and you can’t see an air purifier, don’t be afraid to ask businesses about their HVAC ventilation system and what steps they are taking to keep you safe. HVAC systems are either fresh air or recirculating with the latter not advised as it can recirculate viruses from one room to another. The fresh air system should ideally have their filters upgraded to HEPA to filter out viruses and these HEPA filters must be replaced regularly.

  • At home Keep doors and windows open when you have visitors and have your eye on the CO2 monitor. If you are unable to open the windows, run your HEPA air purifier on high and keep it on high until about 20 mins after your visitors leave.

  • Balancing ventilation with thermal comfort and outdoor pollution Fresh air ventilation is the best