To study the effect of total CFO airflow on ventilation determination and confirm the effect of airflow rate at filter end on measurement of actual degree of ventilation, this Paper first established 3D simulation model of standards flow field for degree of ventilation, by setting the initial condition to simulate, under different total CFO airflows, the simulation calculation value of the same ventilation standards. Meanwhile, it built experimental unit platform for ventilation determination,

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... hich is characteristic of multi-point determination and easy to control airflow rate, and total airflow of filter can be controlled by replacing CFO with different flow rates, thus the actual measurement value of the same ventilation standards can be measured and compared with simulation result of flow. Results show: on the basis of value simulation and experimental verification, CFO with different total airflows (i.e. total airflow at filter end) will have effect on measurement value of ventilation standards. With CFO flow becoming less, the measurement value of the same ventilation standards will become less gradually. When the air volume flow at outlet end of test piece is kept at (17.5±0.3)ml/s, experimental and simulation calculation all verify the maximum deviation of degree of ventilation for standards is 0.19%.