advanced international sensitivity sensing technology, high stability of integrated circuits for the control of the core, using the SMT technology. It is a security products which suitable family, and companies, applicable to detecting the leakage density of indoor gas. When the detected density reaches a setting value, the alarm will send out acousto-optic alarm signal to remaind users to take measures in time. The product has a special design, modern and fashion, small and artistic, and is of convenience to use.