It is a kind of freestanding flammable gas alarm. It adopts advanced gas sensor, and select MCU with high ratio of performance and price as control core. It is a household small type gas security alarm. It can detect gas leak concentration indoor. When gas leak concentration reahes presentting level, the alarm provides a visual and audible signal. When the concentration is below presentting level, the alarm resume to the normal working state, that avoid person loss and property damage lead by toxicosis, explosion and fire because of gas leak.