This invention belongs to the field of gas detection technology, specifically providing a
gas concentration infrared sensor, including a cylindrical body and a circuit board. The circuit board is disposed within the cylindrical body, dividing the cylindrical body into a first space and a second space. An
infrared light emitting component is located in the first space, and an
infrared detection component is located in the second space. A first reflective component is located in the first space, and a second reflective component is located in the second space. The edge of the circuit board has a notch connecting the first and second spaces, and a third reflective component is located at the notch. The infrared light can be reflected sequentially between the first, third, and second reflective components and transmitted to the infrared detection component. This invention can form a double-layered reflective light path within the cylindrical body, ensuring the light
path length while making the outer
diameter and thickness of the infrared sensor smaller than a set value, thus achieving a miniaturized design of the infrared sensor.