The cabin air filter is responsible for providing clean and breathable air to the vehicle’s occupants, it does so by filtering out dirty, unfiltered outside air and channeling it through the climate control system (or the vehicle’s HVAC system). Cabin air filters are the reason why you don’t feel suffocated in your car when you have your windows rolled up and the AC blasted on. Also, it prevents any unnatural outside (or even engine) odor from entering the vehicle cabin.