Smoke alarm

The invention belongs to the technical field of smoke alarms, and discloses a smoke alarm which comprises a base, a mounting groove is formed in the bottom surface of the base, a hollow device body is arranged in the mounting groove, and a communication groove for smoke to pass through is formed in the side wall of the device body in a penetrating mode. A sensor used for detecting the smoke concentration is arranged on the inner top wall of the device body, a controller is arranged on the inner top wall of the device body, the controller is electrically connected with the sensor, a mounting plate is fixed to the inner wall of the device body, and a placement groove is formed in the upper surface of the mounting plate in a penetrating mode; a placement groove is formed in the inner wall of the device body, a first metal sheet is slidably arranged on the inner wall of the placement groove, a second metal sheet is fixedly arranged at the lower end of the inner wall of the placement groove, a buzzer is arranged o