BeST has developed a CO2 monitor at short notice and produced it in a small series, as standard devices are currently not available due to the pandemic.
The concentration of Covid19 viruses in the room air corresponds to the proportion of CO2, as the viruses are exhaled by infected people. Regular ventilation is therefore recommended. However, it is difficult to estimate how often ventilation should take place, as people do not have a sensory organ for CO2 and their intuition is often wrong. This is why devices that display the CO2 content in ppm and also with three LEDs are useful for checking the room air. Usually green (ok) means a value of 400-800ppm, yellow 800-1200ppm and red (ventilation required) over 1200ppm.
As is generally the case with CO2 sensors of this type, the device has to run for about a week so that it can calibrate itself automatically and then provide reliable values. In addition to the four-digit numerical display and the three colored LEDs, there is also a button. At the touch of a button, the display switches between CO2 content in ppm, temperature in °C and relative humidity in %relH.
The room air monitor was developed for and successfully used by Berlin kindergartens.
As CO2 sensor, we use the SCD40 from Sensirion https://sensirion.com/products/catalog/SCD40/
The board was laid out with the software Fritzing https://fritzing.org
The boards were then produced by Aisler BV from Lemiers, Netherlands near the German city of Aachen https://aisler.net
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