A new catalytic converter is compose by a alloy noble metal supported on inert wool and located downstream to combustion chamber appears able to markedly reduce the content of toxic organics, fine particulates and CO emitted by a diesel engine equipped truck. By contrast, emissions of NOx and particulate n-alkanes remain unaltered or increase, according to the driving and operating conditions of the vehicle. Although this tesrs are preliminary the results obtained, however, suggest that the adoption of this device significantly reduce the health risk associated to fine aerosols and carcinogenic PAH. Exhaust concentrations of some unregulated species, e.g. volatile aldehydes, were lowered by the oxidising catalyzer.