If you eat in the library, the residue, debris and even smell of food will attract rats, cockroaches and various insects, which will do harm to books over time. Most foods contain grease, even if you protect the packaging bag, there will still be debris. It goes without saying that the outer wall of cold drink packaging will condense water. There are some precious documents in the library, which need to be preserved for a long time because of poor liquidity. If there are mice, it is a waste of a lot of manpower, material resources and financial resources. In those terrible days of returning to the south, dozens of dehumidifiers in the library were on day and night, just for fear that books would get wet. Even if you borrow it back, in order to better protect the borrowed books, don't get close to food and pollutants.