Air filter is a kind of filter, which refers to a device that removes particles and impurities in the air. It is composed of a filter element and a shell. It is a device to ensure that the air entering the engine is free of foreign matter and fine particles. According to the principle of filtration, air filters can be divided into filter type, centrifugal type, oil bath type and composite type. 

1. The function of the air filter element is to provide clean air for these mechanical equipment to prevent these mechanical equipment from inhaling air with impurity particles during work and increasing the probability of abrasion and damage;
2. The main components of the air filter are the filter element and the housing. The filter element is the main filtering part, which is responsible for the gas filtering. The housing is the external structure that provides the necessary protection for the filter element. The working requirement of the air filter is to be able to undertake high-efficiency air filtration work, not to add too much resistance to the air flow, and to be able to work continuously for a long time;
3. The engine needs to suck in a lot of air during the working process. If the air is not filtered, the dust suspended in the air is sucked into the cylinder, which will accelerate the wear of the piston assembly and the cylinder. Larger particles entering between the piston and the cylinder will cause serious "cylinder pull" phenomenon, which is especially serious in a dry and sandy working environment. The air filter is installed in front of the carburetor or the air intake pipe to filter out dust and sand particles in the air and ensure that sufficient and clean air enters the cylinder.