Issues of Cabin Air Filter- Only System

Issue#1.   Because the cabin filter is located in the outside air intake, mold and bacteria emitted from the evaporator enter the vehicle interior directly without being filtered. This also means that while external contaminants pass through the cabin air filter, the filtered air becomes contaminated again as it passes through the evaporator.  Therefore, the  cabin filter has no effect.                                                                                                                     

Issue#2.   Cabin filters cannot filter the air inside a vehicle in situ. Instead, the air inside is sent to the cabin air filter.       
How does the cabin filter mounted on the air intake filter the air inside the car?                      

Setting recirculation air mode, blocks external intake and instead recirculates the air already in the cabin, filtering out polluted air inside the car and reintroducing it into the car. However, one thing to note is that it only applies to vehicles equipped with a cabin filter in the glove box. Those cabin filter mounted in engine compartment is designed to filter outside air only. So, the recirculated air flows back into the cabin unfiltered.  Therefore, the  cabin filter has no effect.