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This paper describes the development of a CVS compatible sampling system for automotive sulfate emissions. The design resulted from a consensus of ideas from EPA and industry. The system can be used with either a positive displacement pump or critical flow venturi CVS. A mist generator was developed to quantitatively inject sulfuric acid into the tunnel. While sulfate losses were acceptable using the mist generator, with actual automotive exhaust sulfate losses were much higher. The reasons for these losses were investigated. Sulfate losses in the tubing between the car and sulfate tunnel were also investigated.

A baseline testing program was designed and implemented by EPA wherein 78 vehicles were tested in 5 laboratories. The objectives of this study were to 1) obtain sulfate emission factors on a wide variety of different in-use vehicles using current and advanced emission control methods, and 2) determine the effect on sulfate emissions of vehicles meeting increasingly stringent gaseous emissions standards. The program was designed such that the vehicles were divided into the following classes: 1) production non-catalyst vehicles, 2) production catalyst vehicles - grouped according to emissions standards, 3) advanced non-catalyst vehicles, 4) advanced catalyst vehicles, and 5) fleet vehicles.