Precautions for vacuum furnace test

Although the precautions for vacuum furnace have been mentioned many times, today, Nortel Technology still needs to focus on the following points.
Vacuum furnace, as the name implies, means high vacuum value. Because its structure type is circular, it can pump high vacuum value. Why is it necessary to have a vacuum furnace? It depends on the price. Assuming that the vacuum value required by the customer is not high and the atmosphere furnace can meet his requirements, how can he choose. In addition, the atmosphere furnace usually takes in air while taking out air to pass maintenance gas, which can also prevent the atmosphere from entering the furnace and completely meet the requirements of goods processing.