Cabin Air Filters
Cabin air filters clean the outside air from dust, pollens, and other airborne debris before it enters the passenger's compartment. They're found behind the glove box or under the hood by the firewall. Depending on the manufacturer, they're replaced every 10,000 to 15,000 miles.
They can get dirty fast depending on the driving conditions. Driving on dusty roads and other adverse conditions age the filter sooner. They get clogged with debris, restricting airflow as the driver or system attempts to draw in the fresh air. If the fan is set on high and there's little outside airflow through the vents, suspect a clogged cabin air filter.