Can we use the CO2 level in a space to estimate whether ventilation is good or bad ?


Yes, this is a useful technique in a lot of spaces, although it has some limitations. Outdoor CO2 in Australia is about 450 ppm, and human breath increases this concentration. In well ventilated spaces, CO2 should stay below about 800-950 ppm. In poorly ventilated spaces CO2 can reach levels of 3000-5000 ppm. CO2 can be monitored with a smart and affordable monitor.

Example of CO2 monitor with traffic light indicator showing the indoor air quality

The quickest way to lower CO2 level in your working space is by opening a window or turning on the ventilation.

Surveying classrooms, offices etc. with a CO2 monitor can be useful to determine which ones may have the worst ventilation, and prioritizing actions there.

Limitations include:

  • If there are sources of such as cooking they must be turned off for testing
  • The amount of exhaled respiratory aerosols increases CO2 greatly with singing and shouting.

This tech tip is adapted from FAQs on Protecting Yourself from COVID-19 Aerosol Transmission

Learn more about the health benefits of good ventilation in the Harvard Study