The dataset is the synthesized absorbance spectrum of a set of 9-gas mixtures following Beer-Lambert Law. We used the mid-infrared absorption cross-section spectra of C2H6, CH4, CO, H2O, HBr, HCl, HF, N2O, NO from the high-resolution transmission molecular absorption (HITRAN) database. Each sample contains 1,000 observations equally spaced between 1 µm and 7 µm wavelengths. The concentrations of the nine gases are mutually uncorrelated and follow uniform distribution between 0-10 µM.