Photoinductance type smoke and fire detection alarm

The invention relates to a photoelectric inductance type smoke and fire detection alarm which comprises a bottom shell and a fixed seat, the bottom shell is rotatably connected with the fixed seat, the bottom shell is provided with a locking piece for switching states in a circular motion mode, and the fixed seat is provided with a clamping groove which is in sliding connection with the locking piece and can be clamped with the locking piece. The groove wall of one end of the clamping groove is recessed in the direction close to the groove wall of the clamping groove to form a notch part for the locking piece to enter and exit the clamping groove pair. When the locking piece moves to the position coinciding with the notch part, the locking piece is in an unlocked state; and when the locking piece moves to a position clamped with the clamping groove, the locking piece is in a locked state. A user can rotate the bottom shell to enable the locking piece to do circular motion, so that thelocking state and the unl