2 1 Why are there two filter elements for room air conditioning?

2 1 the room air conditioner has two filter elements, because one is inside the car and the other is outside the car. According to the relevant information, we know the location of air conditioning filter elements: in the glove box of the first mate, some models have two filter elements, and there is also a filter element under the front windshield slot, one is the air conditioning filter element inside the car, and the other is the air conditioning filter element outside the car.