Abstract: A system for monitoring carbon monoxide (CO) levels produced by the operation of a vehicle's engine. The system includes a detector in the vehicle's passenger compartment for detecting the concentration of CO inside the compartment and circuitry for generating a HIGH CO signal when the detected concentration of CO inside the compartment is greater than a predetermined level. The system disables the operation of the engine in response to the HIGH CO signal. The system also senses a status condition of the vehicle and inhibits the disabling of the engine when the status condition is sensed.