Automobiles have designed air intakes to allow for ventilation, air flow and climate control. These designed air intakes are located at the lower right windshield area, inside the cowl plenum chamber. These air intakes are located specifically to access relatively clean air for usage inside the passenger compartment.

There also can be undesigned air intakes (body-faults). These undesigned air intakes, if located in an area of negative pressure on the vehicle's perimeter having high dust content, can cause significant dust intake. Most dust leaks occur at lower and rearward vehicle locations. Dust leaks are common in rear wheel housings. In these wheel housings exists an area of high pressure resulting from the action of the turning wheel. Road dust, lifted by the negative air pressure under the vehicle, enters rearward wheel housings and is simply pushed into the vehicle. Almost all dust leaks occur at lower and rearward locations.

Although diagnosis of dust leaks can be assisted by the dust marking the entry location, such diagnosis is hindered by the need to remove interior parts to obtain a guarantee of results.

Consideration should be given to the possible health problems that dust inhalation could cause.