Each person gives off CO2 and aerosols permanently during breathing (liquid particles that can transmit infections). These aerosols and possibly contained viruses cannot be measured directly. However, by measuring the amount of CO2 in a closed room, the aerosol concentration can be closed. The risk of infection can thus also be derived from this and reduced.By means of a complex algorithm, an air quality value based on CO2 equivalent is determined from a composite signal of all the gases determined and represented as a clear traffic light according to WHO-compliant scale. While a "good ambient air" (800 ppm) is indicated by a green LED, a red LED warns when a room needs urgent ventilation or leaving.In addition, the modern metal oxide sensor measures the VOC value, interprets it and displays the value as traffic light.VOCs are hydrocarbon compounds from 2 essential sources: Organic effluents (vapors/odors) from human respiration, perspiration and digestion, as well as vapors of buildin