The job code of health certificate is represented by English capital letters A ~ F'. Where A refers to the person who directly serves customers in public places. B refers to the personnel engaged in the production and operation of drinking water. D refers to employees in the field of food circulation and consumption (including health food production and processing, box lunch production), and E refers to employees in food production and processing enterprises. F refers to others (refers to those who are clearly engaged in the above-mentioned types of work).