concentration obtained by an absorption biased ndir acetylene gas sensor calculating a detected carbon dioxide concentration obtained by an ab ndir carbon dioxide gas sensor calculating a detected water vapor concentration obtained by an ab ndir water vapor ndir gas sensor and then determining the acetylene concentration from the detected acetylene concentration through use of the detected carbon dioxide and water vapor concentrations to compensate for their interference application_number US 201313974587 A description the present invention advances a methodology for the design of an ndir gas sensor system which is capable of detecting sub ppm levels of acetylene gas in transformer oil in the presence of multiple fault gases and moisture in order to achieve a successful methodology a number of technical obstacles must be recognized addressed and overcome the present invention addresses the drawback of ndir gas sensors for detecting gases in the sub ppm concentration ranges having very weak absorption bands located in the far infrared region of the electromagnetic spectrum gt 12 0 u03bc and very unique ultra narrow line shapes and overcomes these drawbacks by a novel ndir design methodology this design methodology comprises 1 matching the ultra narrow line shape of the gas 39 absorption band with a carefully designed narrow band pass filter 2 making sure that the out of band leakage of the filter is not.