This research concentrates on the sensitivity of semiconductor tin dioxide-based gas sensors to hydrogen fluoride in air. After evaluating the characteristic detection temperature, the sensor's signals were studied for different HF concentrations. Despite the corrosive effects of hydrogen fluoride, a reproducibility of the signal was found. Likewise, we did not observe any long-term degradation to the sensor. For the experiment, the sensor was exposed to a gas mixture formed by HF, O-2, N-2 with a constant flow rate of 150 ml min(-1). The semiconductor gas sensor reached maximum sensitivity near 380 degreesC, and a minimum concentration was detected approximately 50 ppb. Moreover, the detection phenomenon appears to be reversible when considering the electrical response under a constant air flow. (C) 2003 Elsevier Science B.V. All rights reserved.