Ford currently offers more alternative fuel vehicles than any other manufacturer. See FFV definition. A colorless, odorless gas which results from incomplete combustion of fuel.
Carbon monoxide is toxic and has adverse affects above certain threshold levels.
It does not accumulate in the atmosphere. These tests certify that vehicles meet the federal emissions and fuel economy standards. Manufacturers test pre-production prototypes of the new vehicle models and submit the results to the EPA, which in turn confirms the accuracy of the figures. To ensure that each vehicle is tested under identical conditions, the vehicles are all driven by professional drivers under controlled laboratory conditions on an instrument similar to a treadmill. So, results can be compared with confidence.