The SGP4x gas sensor platform for VOC and/or NOx measurements is designed as a digital smart switch and regulation unit for air treatment devices such as air purifiers. The sensor’s raw signals are processed by Sensirion’s Gas Index Algorithm, and can be used directly to automatically trigger the removal of indoor air gas pollutants by air treatment devices without the need for user-device interaction. This sensor solution is thus well-suited for constant monitoring of VOC and NOx levels, including potentially harmful events which are imperceptible to humans. Furthermore, automatic control of air treatment devices based on the SGP4x’s signals helps to save energy by turning them off once the VOC and/or NOx events have been taken care of