Gas monitoring is an important issue since the leakage associated with the penetration of gases in the surrounding environment can result in fatalities and harsh consequences. In this work, we propose a novel sensor node architecture for a wireless outdoor CO monitoring unit. To guarantee an autonomous operation, the sensor node is supported by a hybrid power supply, which takes advantage of both wind and solar ambient energy sources to power the node and to charge super capacitors that act as energy buffers. Also, the gas measurement logic is developed such that the energy consumption is minimized. An additional backup energy storage is based on a Li-ion battery. Using an electrochemical CO sensor, we secure the low power consumption of the node without degrading the sensing capabilities. Our solution can be applied for CO monitoring in urban areas and outdoor industrial facilities.