Since the late 1940's automotive engineers and scientists have been conducting research on emission control and developing the results into practical hardware for the four sources of emission from the automobile -- the crankcase, the exhaust, the carburetor, and the fuel tank. It is estimated that 20% of all hydrocarbon losses are divided between the carburetor and the fuel tank and, at present, there is no system available for controlling these losses. The exhaust accounts for 60% of the hydrocarbons and practically all the carbon monoxide. The remaining 20% of the hydrocarbons are emissions from the crankcase. Present control systems make substantial reductions in the emissions from these two sources. Under present levels of control there is a total reduction of about 60% in both total hydrocarbon and CO emissions.
Another factor important to emission control is the need for proper maintenance. Beneficial effects of the installation of an emission control system can be negated if sufficient maintenance is not performed. Between 1968 and 1980 it is believed that research programs on gasoline engines will result in progress toward solution of the emission control problem.