The best time to retain sputum specimens should be before the use of antibacterial drugs, using the second sputum in the early morning. For common bacterial pneumonia, sputum specimens are taken and sent for testing once a day for 2-3 days. Multiple sampling and sending for examination within 24 hours is generally not recommended unless there is a significant change in the appearance and character of the sputum. In patients suspected of having Mycobacterium infection, sputum should be collected for three consecutive days and sputum sent for examination in the early morning. Strictly perform aseptic operations, use special sterile culture cups, and retain sufficient sputum specimens to avoid contamination of normal flora. The sputum specimens should be sent in time to prevent the death or multiplication of the original bacteria in the sputum specimens, preferably within half an hour, not more than two hours. In addition, specimens that are delayed or to be processed should be stored at 4°C and preserved specimens should be processed within 24 hours.