PM25 warning instrument

The invention discloses a PM25 warning instrument. The PM25 warning instrument comprises a shell, wherein a circuit board is arranged in the shell and comprises a PM25 module, a key module, a single chip microcomputer module, a display module and a warning module; the PM25 module is used for detecting the PM25 content in air, converting the PM25 content into an electric signal and simultaneously outputting the electric signal to the single chip microcomputer module; the key module is used for presetting the PM25 content through a key and sending a preset signal into the single chip microcomputer module; the single chip microcomputer module is used for receiving the output signal of the PM25 module, sending the signal to the display module, simultaneously making comparison on the output signal of the PM25 module and the preset signal of the key module and outputting the signal to the warning module and a dust fall module when the output signal exceeds the preset signal; the display module is used for receiving