Air Vision CO2 Indicator Light for Air Quality, with Sensor

Specification

Air Vision displays the CO2 concentration indoors using a indicator light system.
The colour displayed gives a recommendation for ventilation:

Green: Good air quality (CO2 <1000 ppm).
No need for action.

Yellow: Deteriorated air quality (CO2 1000 -1400 ppm).
Ventilation recommended.

Red: Poor air quality (CO2 >1400 ppm).
Ventilation required.
If the status is "red", a warning tone can be emitted.