According to the size of the catering industry, it is divided into large, medium and small. The minimum removal efficiency of oil fume purifier is 61%, 75% and 85% respectively, and the maximum allowable emission concentration is 2.1mg/m3, which is mainly aimed at the oil fume emission management of existing catering units, the design and environmental impact assessment of newly established catering units, and the oil fume emission management during the completion and acceptance of environmental protection facilities and their operation; The staff canteens in food processing units and non-operating units that emit lampblack have no requirements for the emission of lampblack in households. These two standards are aimed at the requirements of lampblack purifier for lampblack treatment, but there is no clear regulation on taste. The height of the fume exhaust pipe should be 1.5m higher than the top of the building where the exhaust pipe is located or attached, and the length of the straight pipe section between the fan and the exhaust port should meet the requirements of the sampling position. Meet the requirements of straight pipe length required by sampling position, and the exhaust port shall not face the susceptible buildings. If there are susceptible buildings higher than the vent outlet within a radius of 21m around the vent outlet of the catering unit. Electrostatic filter: When the gas containing dust particles passes through the high-voltage electric field formed between the cathode wire (also called corona electrode) connected with high-voltage DC power supply and the grounded anode plate, the gas is ionized due to the corona discharge of the cathode. At this time, the negatively charged gas ions move towards the anode plate under the action of electric field force, and when they collide with the dust particles during the movement, the dust particles are negatively charged, and the charged dust particles also move towards the anode under the action of electric field force.