The Incidence and Economic Costs of Major Health Impairments

A control apparatus for use in an engine exhaust gas purification system which includes any combination of an EGR (exhaust gas recirculation) system, an exhaust gas oxidation reactor such as a catalyzer converter, a manifold reactor and/or an afterburner, and a secondary air injection system. The control apparatus comprises devices for detecting engine operating conditions in terms of the temperature of the engine cooling water, the ambient temperature, the internal temperature of the exhaust gas oxidation reactor and the vehicle speed for producing pneumatic signals of atmospheric pressure when the detected information reaches respective predetermined levels, and a selective actuating mechanism including a change-over valve, a one-way valve, an orifice and a passage for logically processing the pneumatic signals of the detecting devices for producing pneumatic signals of positive pressure or of intake manifold vacuum to selectively actuate an EGR control valve and the intake manifold, a change-over valve disposed midway of the exhaust pipe for changing introduction of the exhaust gases between the oxidation reactor and a bypass passage, and a changeover valve for supplying therethrough secondary air to the oxidation reactor.