1. Stability of instruments and equipment: For instruments and equipment with good stability, temporary verification may not be considered; for instruments and equipment with poor stability, verification shall be arranged at an appropriate time;
2. Calibration cycle of instruments and equipment and the results of the last calibration: check the instruments and equipment that the laboratory thinks have a long calibration cycle or the results of the last calibration are not satisfactory at an appropriate time; For the equipment with short calibration period, under normal circumstances, the inspection within the planned time may not be considered;
3. Usage and frequency of instruments and equipment: when the instruments and equipment are prone to failure or after troubleshooting, calibration is not needed; when the instruments and equipment are frequently used, periodic verification should be considered;
4. Use of instruments and equipment: Equipment that is often disassembled, transported and brought to the site for testing and calibration should be considered for inspection within a proper time;
5. Skillful procedures of instrument and equipment operators: Low proficiency of personnel will increase the probability of instrument and equipment failure and even affect the stability of instruments and equipment. Consideration should be given to arranging temporary verification and shortening the interval of temporary verification;
6. Operating environment of instruments and equipment: When the operating environment of instruments and equipment is relatively bad, which affects the use of equipment, periodic verification should be considered.