An air trap is air that is caught inside the mold cavity. It is a bubbles or voids on the surface of the molded product. Converging polymer melt fronts traps it or because it failed to escape from the mold vents, or mold inserts, which also act as vents. Air-trap locations are usually in areas that fill last. Entrapped air will result in voids and bubbles inside the molded part, a short shot, or surface defects such as blemishes or burn marks. To eliminate air traps, modify the filling pattern by reducing the injection speed, enlarging venting, or placing proper venting in the cavity.