Winsen CO2(Carbon Dioxide) Sensor Selection Guide

CO2 concentration Vs. Indoor air quality

CO2 concentration is regarded as one of the most important indicators of air quality in buildings. Closed spaces have increased CO2 concentration than outdoor due to the lack of air exchange. Long stay in such places will cause feeling of dull, dizzy, headache and unable to concentrate. High concentration of CO2 will damage the body, lead to coma or even death. It can also be taken an indicator of air pollution from other possible harmful gases, virus, flu depending on different occasions. Indoor climate plays a key role in health protection, as pathogens remain in rooms for hours at typical air exchange rates in residential and office buildings. An increase in fresh air supply is recommended. The WHO also indicates that CO2 monitoring helps to reduce the Risk of Covid-19 Transmission Indoors.

The amount of CO2 in an air is expressed as parts per million (ppm) – the number of CO2 molecules per million molecules of air.

• 400 ppm: average outdoor air level.
• Below 700ppm: the air is fresh, and people will feel comfortable.
• 700ppm to 1000ppm: the air is still normal although light polluted.In US standard.
• 1500ppm range is critical: the air is polluted with the concentration continue to increase, most people will feel uncomfortable.
• 2000 to 5000ppm: serious air condition and syndrome of headaches, dizzy, stuffy air, poor concentration, increased heart rate and slight nausea.
• Above 5000ppm: this indicates unusual air conditions where high levels of other gases could also be present. Toxicity or oxygen deprivation could occur.
• 40,000 ppm: this level is immediately harmful due to oxygen deprivation.

How to detect CO2 levels?

At room temperature, carbon dioxide (CO2) is a colorless, odorless, non-flammable gas. Detection technologies of sensors are used to monitor CO2 levels at the human presence sites. The most common principles are NDIR non-dispersive infrared and chemical gas sensors. Chemical CO2 gas sensors have the principal advantage of very low energy consumption, but short and long term drift effects, rather low overall lifetime, are major obstacles when compared with the NDIR measurement principle.

NDIR CO2 gas sensors are spectroscopic sensors to detect CO2 by its characteristic absorption. The key elements are a infrared light source, an interference (wavelength) filter, and an infrared detector. The gas is pumped or diffuses into the light tube, absorption of the characteristic wavelength of light is measured.

NDIR sensors are most often used for measuring carbon dioxide due to its high sensitivity and accuracy, stable performance, long life span and affordable cost. However, the light source decline as working time increasing. Winsen has dual channel design that have two rows of elements, will compensate the decline of light source, and realize automatic calibration. To fit different occasions and requirement, Winsen developed CO2 sensors of super low power consumption, improved accuracy, economic cost, optional measurement range for varying demands(to be found in below applications).