Scroll air compressors use a pair of spiral-shaped scroll pieces to compress the air. One scroll is stationary, while the other is fitted inside the stationary scroll and moved in a tight circular motion without rotating. The orbiting scroll then presses against the inside of the stationary scroll, pushing and trapping air into small pockets between the two. These air pockets are moved through the spiral towards the center, becoming smaller and compressing as they move through the process. Once the pockets have reached the center of the spiral, they are sent through a discharge pipe for use in the end process. Scroll compressors are oilless by design, as the pair of spiral scrolls never make contact with each other. The only vital maintenance required for scroll compressors is a regular filter change.