When the use of instruments and equipment is harsh, it will affect the use of equipment, and it should be considered to arrange a period of verification. When the proficiency of personnel is not high, the probability of instrument and equipment failure will increase, and even sometimes affect the stability of the instrument and equipment, should consider arranging period verification and reducing the interval of period verification. For instruments and equipment identified by the laboratory that the calibration cycle can be longer or the last calibration result is not very satisfactory, the instruments and equipment should be checked during the appropriate time arrangement; For instruments and equipment with short calibration cycles identified under normal conditions 1, it is not considered to arrange period verification. Equipment that is frequently disassembled, transported, and carried to the site for testing should be considered for scheduling periodic verification when appropriate. When calibration is not necessary during the period when the instrument and equipment are prone to failure or after the fault has been rectified, it should be considered to arrange a periodic check. Next, several common ways of instrument measurement calibration: 1, the use of different methods to compare, such as the result of the instrument method and chemical method. 2, compare the quantity value with the same another device or several devices: the laboratory often has multiple identical or similar instruments, and can use multiple instruments and equipment of the same model to compare the reproducibility test of the same project; If there is only one instrument, it can be compared with other laboratory instruments. 3. Participate in the inter-laboratory comparison and capability verification plan, and if the results are satisfactory, the measurement value of the instrument is normal and reliable. 4, the use of certified standard materials for verification: standard materials include a variety of standard samples, standard instruments. If the balance is checked using standard weights; Gas monitor with standard gas verification; The noise monitor is checked by sound calibrator; The specific operation is to use the standard material to calibrate the parameters of the instrument and equipment to check whether a certain parameter or quantity value measured by the instrument and equipment is within the controlled range. 5. Retest strictly controlled retained samples (retained samples retest): As long as the retained samples are stable, they can also be used as the standard for verification during the period. This method can be used when the laboratory does not have a reference standard and there is only one equipment to be examined.