Hygiene engineering is considered a subject that is easy to deal with in the field of practical practice, but it has many post-op problems that mean that the technology is not as deep as it is. The book says that the whole process from the development of sanitation technology to the testing and testing is highly detailed, especially by simplifying all the data based on the NPC, which has been the basis for our country's sanitation system, so that we can even serve as a key point to help build a