What motor vehicles are permitted to enter an environment zone without a fine-particle badge?

In Germany, environmental zones (Umweltzonen) require vehicles to display a fine-particle (Feinstaub) badge to help reduce air pollution. However, certain vehicles are exempt. All two- and three-wheeled motor vehicles (like motorcycles and scooters) are allowed without a badge because they generally produce less pollution and are less frequent in these zones. Similarly, agricultural and forestry tractors are exempt due to their special use and limited impact within these areas. Other vehicles, including those with catalytic converters, must display a valid badge to enter without a fine. This rule helps balance environmental protection with practical use for specific vehicle types.