As a relatively new function in the automotive field, in-vehicle air filters are often overlooked in daily vehicle maintenance. This is unfortunate, because cabin filters are as important to passengers as engine air filters are to vehicles. The cabin filter processes the air that enters the passenger compartment through the vehicle's heating and air-conditioning system, and improves passenger comfort by trapping particles, pollen, and other irritants. For people with allergic reactions and other sensitivities to airborne pathogens, cabin filters represent a major advancement. The replacement cabin air filter is designed to optimize airflow and filtration and fully meet all OE requirements. Up to five layers of filter media are used to capture impurities as small as 0.001 microns. Just like the engine air filter.