This paper studies the response characteristics of an odor sensor based on organic thin-film transistors (OTFTs) obtained from spin-coated poly-3-hexylthiophene (P3HT) on a thermally grown SiO(2)/Si wafer. The response characteristics of the odor sensor based on OTFTs are measured for odor gases generated from liquid fumes of 2-mercaptoethanol and 3-methylindole, such as are typically emitted by pig slurry in ambient air conditions. The experiments show that the response characteristics of the OTFT, when exposed to the 2-mercaptoethanol and 3-methylindole gases, result in a threshold voltage shift, a change in drain current, and a change in mobility with the gate bias. (C) 2011 Elsevier B. V. All rights reserved.