A convection oven differs from a conventional oven in that it has a fan to circulate air in the oven cavity. The air circulation helps to distribute heat evenly within the oven, resulting in faster and more even cooking.
All ovens use radiant heat to cook food. In conventional ovens, the heat is usually supplied by heating elements in the top and bottom of the oven cavity. The top element is used for broiling, while the bottom element is used for baking and roasting. Because the heat is coming from one direction, the part of the food nearest to the heat source cooks more quickly. This is especially troublesome when there are two or more racks of food being cooked at the same time. Convection ovens solve this problem by circulating hot air to all food surfaces, which makes them good choices for cooking in bulk. The best convection ovens have a third heating element that heats the air drawn in by the fan to ensure even heating throughout the oven cavity.
Convection ovens usually need less cooking time and lower temperatures to cook a given amount of food than a conventional oven needs. Other advantages of using a convection oven include reduced food shrinkage and less risk of partially burned or undercooked food.