Abstract: An oxidation or converter apparatus for cleansing air contaminated by volatile organic compounds (VOC) in an exothermic reaction includes a first pipe connectible to a source of the VOC contaminated air and a combustion chamber with a burner, an inlet for the VOC contaminated air and an outlet to atmosphere for exhaust, the inlet being connected to the first pipe. A catalytic oxidizer having an inlet for the VOC contaminated air and an outlet to atmosphere for exhaust is also provided along with an air-to-air heat exchanger. The outlet of the catalytic oxidizer is connected to a first inlet of the heat exchanger in order to provide heated exhaust air to one side of the exchanger. A second inlet of the heat exchanger is connected by a suitable conduit to the first pipe. The contaminated air which is preheated in the heat exchanger is carried by a further conduit to the inlet of the combustion chamber.