Milled hairy glass nodules in the lungs are potentially infectious. If a patient’s hairy glass nodules are caused by a virus or mycoplasma infection, they are clinically contagious. If the patient’s hairy glass nodules are caused by bacteria, they are not clinically contagious. If a patient has a benign nodule or a malignant nodule, it is not clinically contagious. Therefore, when a patient has a pulmonary hairy glass nodule, it is necessary to combine clinical symptoms and further examination to clarify the nature and cause of the nodule. If the nodule is due to a bacterial infection, antibiotic therapy is indicated. If the nodule is due to a viral infection, antiviral and symptomatic treatment is required. If the nodule is caused by a mycoplasma infection, a macrolide antibiotic or a quinolone antibiotic is indicated. If the patient has a benign nodule, it should be reviewed regularly. If the patient has a malignant nodule, surgery should be considered.