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CO2 monitoring in commercial spaces is a cost-effective way to manage spread of Covid-19 through optimising ventilation.

Poorly ventilated spaces increase the risk of virus transmission. Yet, it can be difficult to manage effectively because air is invisible, making ventilation a less obvious mitigation measure.

Monitoring indoor CO2 concentration is a useful proxy for understanding occupancy levels and ventilation rates, since it represents the fraction of air that has been exhaled by people within the room. Whilst it is not a direct indication of infection risk, it can be a cost-effective way of identifying spaces with poor ventilation which require improvements to be made.

Many existing buildings are naturally ventilated which means that in winter it can be difficult to balance ventilation rates with maintaining thermal comfort (without significantly increasing energy use). For naturally ventilated buildings, in colder months, windows and vents do not need to be opened as wide because the wind and temperature difference between inside and outside is greater, driving air through openings. It is better to open all windows and vents a small amount rather than opening only a few.

CO2 sensors are available from a number of suppliers, costing as little as £150 per space monitored, and come with easy-to-understand web interfaces. Monitoring of the CO2 level against the WELL standard of 750 ppm enables windows to be opened and closed or narrowed as appropriate thus achieving an air change rate that balances infection risk with energy use.

Figure 1: Example output – Hodkinson office on 19th October 2021