A convection oven has a fan installed to circulate the hot air in the oven. True convection ovens have a third heating element that heats the air before it enters the oven. Manufacturers also sell models that add the fan without the third element.
Traditional radiant ovens cook by surrounding food with heat produced by a flame or heating element. Moving the air inside a convection oven increases the rate of heat transfer from the air to the food. The faster heat transfer increases the browning for meats and creates crisp pastries.
Cooking with a convection oven require adjusting recipes. The cook has the option of reducing the cooking temperature by 25 degrees and maintaining the same cooking time as with a radiant oven, or cooking at the temperature setting the recipe recommends and reducing cooking time by approximately 25 percent.
Convection ovens work best when cooking uncovered dishes. Covering the food reduces the heat transfer, as the food is no longer in contact with the air currents. If the oven offers the option of convection or radiant heat, cooks should select the radiant heat option for covered dishes. Removing the cover midway through cooking and switching the oven to the convection setting creates evenly browned casseroles.