A gas-sensor arrangement for measuring a target-gas concentration has first and second NDIR emitters to one side of a space containing the target gas and projecting respective first and second beams of infrared light through the space. An it receiver on the other side of the space and irradiated by the first and second beams for emitting first and second outputs respectively corresponding to the first and second beams and together forming a receiver signal corresponding to radiation received from the first and second beams. One of the emitters is optically farther from the receiver than the other of the emitters. A filter between the receiver and the space is traversed by the first and second beams and permeable only to radiation of a wavelength range corresponding to the target gas. A controller connected to the radiation receiver calculates the target-gas concentration on the basis of the receiver signal.