Why can convenience store microwave ovens be used for free?

Only the goods that need to be heated in the convenience store itself can be heated for free, and the food that comes with it cannot be heated.

The use method of microwave oven is to put the microwave oven flat in a ventilated place, which is beneficial to the heat dissipation effect of microwave oven. When heating food in the microwave oven, be careful not to put too much food, otherwise it may cause the inside of the microwave oven to be crowded and cause an accident. When using microwave oven to heat, we should pay attention to the heating time, because the temperature in the microwave oven is very high, and too long time will scorch the food, which will lead to the danger of fire.