Filtering device convenient for replacing filter cartridge

The filtering device comprises a shell, a sealing piece A, a sealing piece B, a sealing piece C and a filtering piece, an air inlet cavity and an air outlet cavity are formed in the shell, the shell is provided with an air inlet communicated with the air inlet cavity and an air outlet communicated with the air outlet cavity, an opening A communicated with the air inlet cavity is formed in the side wall of the shell, and an opening B communicated with the air outlet cavity is formed in the side wall of the shell. The upper end of the shell is provided with an opening B communicated with the exhaust cavity, the lower end of the shell is provided with an opening C communicated with the air inlet cavity, the sealing piece A is used for controlling on-off of the opening A, the sealing piece B is used for controlling on-off of the opening B, the sealing piece C is used for controlling on-off of the opening C, and the filtering piece is connected to the shell and located in the air inlet cavity. An operator can dire