At present, there are 2 emission standards for kitchen fume purifiers, one is the local standard and the other is the national standard. The national emission standard is that the concentration of emitted oil smoke needs to be less than 2.0mg/m3, in some places, like Zhengzhou, Beijing, Shenzhen, Shanghai, etc. In addition to complying with the requirements of the national standard, the local standards are also enforced, and the concentration of emitted oil smoke is less than 1.0mg/m3, in addition to the requirement of purification of particulate matter and non-methane hydrocarbons.