Abstract: A sensor system is provided for pressure vessels. In one embodiment, a compressor directs compressed air into a purification chamber for removing carbon monoxide from the air. A sensor system housing is fastened to an opening on the purification chamber. The sensor housing provides an electrochemical sensor driven by an independent power supply and an electronic processor for receiving a signal from the electrochemical sensor. If the carbon monoxide in the purification chamber reaches a predetermined level, the electronic processor is programmed to initiate a shutdown of the compressor utilizing a relay cable.