Abstract A gas chromatographic method for the determination of lower fatty acids as odour pollutants is discussed. A sample gas was introduced on to glass beads coated with 1% sodium hydroxide solution to collect fatty acids, which were isolated in a sampling tube and then submitted to gas chromatography without concentration. These fatty acids were reacted with trimethylsilylimidazole to form trimethylsilyl esters, which were also subjected to gas chromatography. The latter method resulted in a sensitivity 5–10-fold greater than that by the former method. The recoveries were more than 90% in both methods, with coefficients of variation of less than 5% in the former and about 8% in the latter. The gas chromatographic method gave good reproducibility, with detection limits of 0.5–1 ppb when 200 1 of gas were sampled. Air quality was determined by both the methods on samples from a hog farm and a refuse incinerator.