Automotive Emissions After Hot and Cold Starts in Summer and Winter

Randomly selected passenger automobiles were driven over a 7.5-mile composite route in Cincinnati, Ohio. Samples of the exhaust gases were collected from each car by means of a proportional sampler and analyzed for gross hydrocarbons, carbon monoxide, carbon dioxide, and oxides of nitrogen. In addition, detailed analysis of the hydrocarbons was made. This included parafins, 1 through 8 carbon, olefins, 2 through 6 carbon, and aromatics, 6 through 10 carbon. This paper compares the differences in these emissions immediately after starting with “cold” engines as opposed to emissions from cars started with engines already warmed up or “hot.” This determination was made under both cold and warm weather conditions. A comparison is also made in air pollutants emitted from cars driven under the summer as opposed to the winter conditions normally encountered in Cincinnati, Ohio.