Abstract: A catalytic converter for controlling unburned emissions from automotive exhaust gases includes a reactor chamber having inlet and outlet openings for passage of the exhaust gases therethrough. Oxidizing catalyst devices are distributed along the reactor chamber between the inlet and outlet openings for contact by exhaust gases flowing therethrough. Secondary air feed means is provided for feeding secondary air into the reactor chamber at a plurality of spaced-apart locations between the inlet and outlet openings. The secondary air feed means includes a conduit extending in a tortuous path through the reactor chamber for pre-heating secondary air flowing through the conduit prior to discharge into the reactor chamber. The flow rate and distribution of secondary air are arranged to prevent overheating of the catalyst. Malfunction of the converter is detected by comparing temperatures in the last two stages or by sensing the absolute temperature of the last stage.