Abstract: According to the provisions of AQ 6201—2006 coal mine safety monitoring system for general technical requirements,when gas concentration in coal mine driving roadway is more than or equal to 3.0%, local fan stops running; when two conditions are met, local fan is blocked and closed to prevent "Chui". In the implementation and use of the function, control logic design is unreasonable, and field application is not easy to realize, which is easy to cause wind machine stopped by mistake and unable to carry out periodic calibration test. Taking KJ100NA safety monitoring system and Linnancang Mine as an example, "3.0% blocking" control design and field realization are elaborated.