These aerosols and potentially contained viruses cannot be measured directly. However, by measuring the amount of CO2 in a closed room, one can infer the aerosol concentration. This allows for the derivation and reduction of the infection risk. A complex algorithm calculates an air quality value based on CO2 equivalent from a summation signal of all detected gases and presents it in a clear traffic light format according to WHO standards. While "good indoor air" (below 800 ppm) is indicated by a green LED, a red LED warns when a room urgently needs to be ventilated or vacated. Additionally, the modern metal oxide sensor also measures the VOC level, interprets it, and displays the value as a traffic light. VOCs are hydrocarbon compounds from two main sources: bio-effluents (emissions/odors) from human breathing, perspiration, and digestion, as well as emissions from building materials (carpets, paints, adhesives, etc.) and furnishings (furniture, printers, copiers, etc.) or even cleaners, perfumes, and cigarette smoke. While simple CO2 sensors do not detect or respond to these substances, this is possible with the modern semiconductor sensor and its VOC/CO2-eq sensor algorithm. This makes the product an "air quality sensor" and signals poor air quality even in situations where simple CO2 sensors fail. VOCs can cause eye irritation, headaches, fatigue, and dizziness, which are summarized under the term SBS (Sick Building Syndrome). With the reliable information from the sensor, healthier conditions for individuals in enclosed spaces can be created in the future. With the sensor, you will always know exactly when the indoor air quality and thus the risk from viruses exceeds a critical threshold.