Fire detector

摘要

Fire alarm comprises a field effect transistor gas sensor with a source region (S), a channel region (2), a gate electrode (7) and a drain region (D). The gate electrode has one or more gas sensitive layers so that the channel conductivity of the transistor can be controlled depending on the gases to be detected. Preferred Features: A gap (26) is provided between one channel and the gate electrode for detecting the gas. The gas to be detected chemically reacts with the gas sensitive layers.