School sensor of indoor air quality NLII-CO₂-R-5-A with an alarm is used to monitoring indoor air quality in school buildings (school class) and for controlling of ventilation units based on actual concentration of carbon dioxide (CO₂). It is suitable for WELL Building standard buildings. NLII-CO₂-R-5-A is special CO₂ sensor designed for schools, with extended measuring range from 400 ppm to 5000 ppm and with built in alarm. Sensor is used to monitoring indoor air quality in classrooms and for controlling of ventilation units based on actual concentration of carbon dioxide (CO₂).