The biggest harm is carcinogenic, when the oven temperature exceeds 200 degrees Celsius, the food is easy to produce heterocyclic amines, benzopyrene and other carcinogens, often eaten on the human body will be harmful. So in the use of the oven, should try not to bake some of the food need a very high temperature. If you need to bake meat, you can turn down the baking temperature and make it cooked by extending the baking time. This can not only avoid food cancer, baked texture and flavor is also very good. Selection of the oven is as follows: 1, look at the capacity, the general capacity of the electric oven ranges from 9 liters to 60 liters, choose the capacity of the oven, it is necessary to sub-consider the use of buying an oven and their own needs. If you just bake some snacks for the family, just choose 9 to 12 liters is enough. If the family population is relatively large, the frequency of use is high, you can choose large-capacity products. 2, look at the power, generally the higher the power of the oven has a faster warming speed, heat loss less characteristics, will be more power saving. So the general family, it is recommended to choose close to 1000 watts above the oven as well. 3, look at the safety, in the purchase is, need to pay attention to whether the oven has heat insulation performance and light transmission performance, and whether it has good sealing and so on. 4, ease of operation, the operation of the cumbersome electric oven will not be convenient to use. And a simple and easy to use oven will alleviate a lot of the process. Oven use methods and precautions are as follows: 1, when the oven for the first time before use, you need to use warm water to clean the grill and baking tray, and wipe the inside of the oven with a soft damp cloth soaked in detergent. Then wait for it to dry completely, bake the oven empty for a few minutes, after which it can be used normally. 2、When baking food, the oven should be placed on an insulated horizontal tabletop, with enough space around it, and no objects should be placed on the top of the oven. 3, when using, according to the variety and weight of food to properly adjust the cooking time. In case of frozen food, you need to thaw it out before baking. In baking food should remember to turn over to make it evenly heated, and secondly in the electric oven work, can not frequently open the door, so as to avoid heat dissipation. 4, in the use of the oven baked food, it is best to add a little water in the baking dish, so as not to take away the food moisture at high temperatures, baked food is too dry, too hard. 5, after the use of the oven, be sure to do a good job of cleaning in a timely manner, cleaning the oven before, first unplugged and wait for the oven to be completely cooled before proceeding. When cleaning, do not use sharp cleaning tools, so as not to damage the non-stick coating of the baking pan.