Abstract: An assembly for removing substantially all oil contamination from bleed air flowing at a temperature of the order to 600-650 degrees Fahrenheit from a bleed air port of a gas turbine aircraft engine to a duct leading to the cabin ventilation system of an aircraft. The assembly comprises a gas turbine engine and a catalytic converter interposed between and sealably coupled to the bleed air port of the engine and the ventilation duct, at a location near the engine. The catalytic converter comprises at least one catalytic converter matrix element through which the bleed air must flow at high temperature and at a mean velocity, each matrix element comprising a parallel array of slender tubules, which are coated internally with a catalytically active coating which produces oil-breakdown at the temperatures and residence time produced by the engine at continuous maximum thrust.