Why is there a foul smell in the car?

[Frank]

The odor in the car originates from the vehicle itself. The following are the causes of the odor: 1. Car interior: The extensive use of materials such as plastic, rubber, fabric, paint, insulation materials, and adhesives in the car interior is one of the sources of the odor, especially in new cars. 2. Odor caused by the air conditioning: When the car air conditioning is operating, impurities in the air are filtered out by the evaporator's cooling fins and then discharged along with the condensate. If these impurities and condensate remain on the surface of the evaporator's cooling fins, fresh air passing through the fins can produce an odor. 3. Dirty evaporator box: The environment inside the evaporator box is relatively humid. Dust in the air and fallen leaves from parking under trees that are not cleaned in time can cause the ventilation lines and the evaporator box to become dirty, leading to an odor. 4. Asphalt damping sheets: The smell from the original asphalt damping sheets is also a major source of odor. Turning on the heater in winter increases the temperature inside the car, causing these toxic gases to volatilize.