I can recommend against one type of bad sensors. VOC sensors paired with a temperature sensor that can generate “eCO2” value is known bad, such as CCS811/BME280 combo board.
Those sensors guesstimate CO2 concentration from air temperature and changes in ambient alcohol/acetone/hydrocarbon levels, which drifts into positive infinity and is simply do not correlate well with actual CO2 level.
Those sensors are dirt cheap, and can still be used as a rule of thumb to encourage regular ventilation, but are nothing more than that. If you want to actually see CO2 levels, avoid those.
Those sensors guesstimate CO2 concentration from air temperature and changes in ambient alcohol/acetone/hydrocarbon levels, which drifts into positive infinity and is simply do not correlate well with actual CO2 level.
Those sensors are dirt cheap, and can still be used as a rule of thumb to encourage regular ventilation, but are nothing more than that. If you want to actually see CO2 levels, avoid those.