Gas sensor modules with a performance difference. Sierra Monitor gas sensor modules provide continuous trouble-free monitoring of hazardous gas conditions to protect your personnel and facility. Sierra Monitor integrates extensive gas sensor technology with electronics expertise to offer a broad line of diffusion gas sensor modules. The modules condition the sensor signal and provide an industry standard 4-20 mA output that can interface with single or multichannel controllers and distributed control systems. Sierra Monitor employs catalytic bead, electrochemical, semiconductor and infrared technologies to match the appropriate sensing technology with the application requirement.