A portable electronic device includes a casing and an actuating and sensing module. The casing includes at least one inlet aperture, at least one vent aperture, a first chamber, a second chamber and at least one communication channel. The communication channel is connected between the first chamber and the second chamber. The actuating and sensing module includes an actuating device and a sensor. The actuating device is disposed within the first chamber and closes the inlet aperture. The actuating device further includes a first protective film. The sensor is disposed within the second chamber. When the actuating device is enabled, a gas is guided into the first chamber through the inlet aperture, and the gas is transferred to the second chamber through the communication channel so as to be monitored by the sensor. After the gas is monitored, the gas is outputted from the vent aperture.