Over the past year, we have frequently heard about the importance of ventilation and how easy it is to measure the level of CO2 in the air. But are these topics directly related to the Covid-19 pandemic or does it just highlight the importance of these measures?
Does measuring the level of CO2 indicate the presence of the Covid-19 virus?
Measuring the level of ambient CO2 gives an indication of the rate of air renewal in a closed room. Thus, when several people breathe in a room, the level of CO2 increases, thereby the amount of micro-droplets suspended in the air increases.
Therefore, this measurement does not detect the presence of a virus, whether it is influenza or Covid-19, but can indicate the ventilation rate of the room and the presence (or even the increase) of agents facilitating contagiousness.
How do you measure CO2?
Historically, the measurement of CO2 was done by optical interferometric measurement in the infrared. These NDIRs (non-dispersive infrared sensors) are very sensitive spectroscopic sensors commonly used for gas analysis. They have the advantage of being very specific, but their size and cost is often a downside.
Recently, a new CO2 sensor is available allowing miniature low power devices for CO2 measurement. The sensor, marketed by Sensirion, uses a photoacoustic technique and is very easy to integrate into product development projects.
Finally, we can also measure the level of CO2 in the air using estimated CO2 sensors that use MOX (metal oxide) semiconductors or polymer sensors. These very inexpensive and miniature sensors do not measure CO2 directly, but indirectly estimate the concentration of the latter by measuring other gases (h2 or VOC). They are very effective in measuring the quality of the air in general.
Is it expensive to do this for a commercial / professional space?
There is a wide range of prices and devices for measuring CO2: prices can be in the range of $ 100 to $ 5,000. New miniature and low-power technologies make it now possible to analyze the level of CO2 with portable and connected devices for as low as $ 250 to $ 350.
Is measuring the level of CO2 also relevant for other reasons?
By measuring the level of CO2 in the air of buildings, houses and apartments, we are actually measuring the rate of renewal of indoor air. This measurement is therefore very relevant for improving the quality of ambient air and preventing the accumulation of gases such as VOCs at concentrations that can be harmful to humans.
The Sensirion CO2 sensor also gives the temperature and relative humidity, which could be used for environmental monitoring of greenhouses crops.
Many advances in miniaturization and cost reductions have been made in recent years in the field of CO2 sensors. Thus, it is possible, at low cost, to measure air quality in order to prevent situations that could cause harm to health for people who spend several hours a day in closed environments.