Carbon monoxide from motor vehicle exhaustcarbon monoxide from exhaust of combustion engine of motor vehicle not in transitcarbon monoxide from exhaust of motor vehicle not in transitcarbon monoxide from farm tractor exhaust when not in transitcarbon monoxide from motor vehicle exhaust in garageexhaust gas of automobile not in transitexhaust gas of motor vehicle not in transitmotor vehicle exhaust when motor not in transitvehicle exhaust fumes