Air Filters - Paper: Air filters found in most 'production cars' are made from paper (as filtration) and plastic as the body.

Paper filters are a stacked matting of fibers creating a random weave approximately 1/2mm thick, and rely on the "screening" effect to stop dirt particles. Airflow per square inch is so poor that the paper must be pleated using many feet of material to make a filter. All dirt or dust particles must be caught on the surface or not at all. Each time a particle is caught, it stops up a hole. From the moment you start your engine, you have a rapidly decreasing air flow rate. Paper also has two other big drawbacks for off-road use. Any moisture reaching the element causes the fibers to swell, reducing airflow even more. Another is the possibility of rupture. Paper is not a very strong material, especially where it is creased to form each pleat. Intake manifold backfires, or cleaning attempts with compressed air, usually rupture the paper leaving the filter ineffective.