A research group led by Associate Professor Yo Ishigaki of the University of Electro-Communications verified the accuracy of an inexpensive carbon dioxide concentration measuring instrument (CO2 sensor) sold on the EC site as a countermeasure for the new coronavirus infection. Most did not react to CO2 and strongly reacted to disinfectant alcohol.There is a possibility that a device equipped with a pseudo sensor is on the market.
In order to prevent the spread of the new coronavirus, the measurement and visualization of indoor CO2 concentration is attracting attention as a measure of ventilation and the degree of crowding of people.On the other hand, the handling of inexpensive CO2 sensors is increasing rapidly on EC sites, but it is generally difficult to check the sensor accuracy.
The research team purchased 2,900 sensors for 4,999-12 yen sold for infectious disease control at a major EC site for accuracy verification.A sensor was enclosed in an acrylic water tank, the CO2 concentration in the water tank was changed, and the displayed value was recorded.As a result, 3 models (25%) could be used for CO2 measurement if adjusted correctly, and 1 model (8%) was considered to be out of order. Eight models (8%) responded strongly to alcohol rather than CO67 concentration, so they are equipped with a pseudo sensor that measures substances other than CO2.
In infectious disease control, if the sensor displays an erroneous undervalue, proper ventilation and behavior change will not occur.On the other hand, if the display of an excessive value continues, the user's sensor display may be ignored or indifference may occur.
Therefore, this time, the research team proposed a simple confirmation method for the purchased sensor.It is (1) to display around 400ppm in fresh outdoor air, (2) when the sensor is blown, the concentration (ppm) rises to the measurement limit value described in the instruction manual, (3). The CO2 concentration does not increase even if the hand sprayed with rubbing alcohol is brought close to the sensor.If it cannot be confirmed, it is recommended not to use it as a ventilation monitor as a countermeasure against infectious diseases.
