A quantitative determination was conducted to determine the concentration of six mixtures in ambient air. The components of the two to six substance mixtures were present in concentrations ranging from 50 to 100 parts per billion. The analytical method used was fourier transform/infrared spectroscopy (FT-IR). Evaluations were made of the optimal least squares fit method selected, background reference file chosen, and quantitative peak windows picked. For some of the components, the FT-IR method was accurate to the 0.1 part per million (ppm) level. For other determinations accuracy was attainable to the 50, 10, and 1ppm levels. The six components in one mixture studied included 2-propanol, (67630) ethyl-ether (60297), 3-chloropropene (107051), styrene (100425), ethylbenzene (100414), and Freon-11 (75694). Other mixtures consisted of toluene (108883), 1,1,1-trichloroethane (71556), 1,4-dioxane (123911), acetone (67641), and 1,2-dichloroethane (107062); vinyl-chloride (75014), benzene (71432), methylene-chloride (75092), 1,1- dichloroethene (75354), and trichloroethene (79016); 2-butanone (78933), hexane (110543), 4-methyl-2-pentanone (108101), tetrachloroethylene (127184), and 1,4-dioxane; cyclopentane (287923), ethyl-acetate (141786), 1,1-dichloroethane, 1,1,2- trichloroethane (79005), and carbon-tetrachloride (56235); and chlorobenzene (108907) with o-chlorotoluene (95498). The authors conclude that FT-IR spectrometry can be used to identify and quantify the industrial compounds present in multicomponent mixtures.