How is an environmental zone monitored in France?

Environmental zones in France are primarily monitored by local councils and national police. Officers check both moving and parked vehicles. In some French cities, there is even a dedicated traffic service operating within these zones. For instance, in cities like Paris, they use cameras to determine the emission class of vehicles. Through automatic number plate recognition, they can identify vehicles that violate the rules and check if they qualify for any exemptions. However, this system only works for French vehicles as they do not have access to data on foreign vehicles. Vehicles without an emissions sticker in an environmental zone may receive a fine (in accordance with article R.411-19-1 of the French traffic code).