Can the laboratory only use indoor single quality control?

You can't. Indoor single quality control refers to the use of standard substances with known concentrations in the laboratory to verify the accuracy and precision of analytical methods and instruments in the laboratory. We can only check whether the analysis process inside the laboratory is correct, but we can't check the comparison and cross-validation between the laboratory and the external environment. Therefore, in order to ensure the effectiveness of the laboratory quality control system, outdoor quality control is needed, that is, comparison and cross-validation with other laboratories, not just indoor quality control.