Air Flow Sensor and Optional Device That is for Electrical Machine

An air flow sensor includes a case (26), a to-be-detected object (27), and a detector (28). The case includes an intake port (26a) and an exit port (26b) through which air is to flow. The to-be-detected object is located at a first position in the case when the air flowing from the intake port to the exit port has lower than a predetermined level of pressure, and is movable from the first position receiving the air when the air has equal to or higher than the predetermined level of pressure. The detector is disposed outside the case and is configured to detect a movement of the to-be-detected object and output an electrical signal. 本发明提供种空气流传感器和具备该空气流传感器的电器设备用选装装置，能够以低成本的简单结构实现，且适于用于检测来自图像形成装置的排气这样的弱风(空气流)。空气流传感器具备：具有作为空气流的入口(26a)及出口26b)的各开口的壳体(26)；在壳体内承受从入口(26a)向出口(26b)流动的空气流而进行悬浮移动的被检测体(27)；设于壳体(26)的外侧，检测被检测体(27)的移动并输出电信号的检测器(28)，在空气流低于规定的风压的情况下，被检测体(27)位于第位置，在空气流在规定的风压以上的情况下，被检测体(27)从第位置移动。当空气流低于规定的风压时，被检测体(27)由于其自重而返回第位置。