Why measure CO₂?
Knowing the CO₂ level in the inside air will help you protect yourself and others from getting COVID-19 or other respiratory diseases. It will also help you avoid excessive sleepiness and poor concentration from high CO₂ levels.
Why is that?
We all breathe in oxygen and breathe out CO₂, which means the CO₂ level in an indoor space increases over time, depending how many people there are in the room and how well it is ventilated.
That means the CO₂ level in an indoor space gives an idea of how fresh or stale the air is.
If the CO₂ level is too high, it means the air is stale and the space needs more ventilation.
The more stale the air is, the greater the number of germs, such as coronaviruses, in each breath, so the more likely you are to become ill.
As well as increasing the chance of catching an infectious illness, a high CO₂ level makes you sleepy and affects your ability to do complex tasks, like driving a car, flying a plane or doing maths.
Why CO₂ level is a trustworthy indicator of air quality:
Professor Joseph G Allen talks about what the CO₂ level in a room
actually means:
It’s not just about preventing infection, but also improving performance. This excellent study from 2018 by University of Harvard Professor Joseph G Allen showed how pilots perform less well as the cockpit CO₂ level goes up, even to levels that are not all that high:
It’s not just about preventing infection, but also improving performance. A heightened CO2 level can reduce the brain’s cognitive function by more than 50%. Click on the picture to read this study from 2016:


