The reliability and lifetime distribution of indirect-heating gas sensors used for detecting butane gas are investigated. The reliability and the operation-lifetime test are carried out in the way that is the same as other electronic devices. Through the numerical analysis and data processing of the failure data, the lifetime distribution, distribution parameters, and reliability level are obtained. For SnO2-gas sensors, the lifetime distribution is the logarithmic normal distribution, and the mean lifetime is about 13,052 h. However, for CdSnO3-gas sensors, the lifetime distribution is the Weibull distribution and the reliable lifetime and mean lifetime are about 1756 and 10,772 h, respectively. The results indicate that different sensitive materials have different lifetime-distribution types, and SnO2-gas sensors are more stable and reliable than CdSnO3-gas sensors. [Copyright &y& Elsevier]