Abstract: A method and an apparatus for inactivating contaminants in blood products are disclosed. The blood product is flowed past an emitter of type C ultraviolet radiation while controlling the flow of the blood product so that the irradiation doses which are received by the blood product are lower than 640 joules/m2. The blood product is substantially free of nonenveloped viruses after the irradiation. The apparatus includes an emitter of type C ultraviolet radiation placed so as to emit the type C radiation toward the blood product in a quartz tube or a tube made of polymerized material which does not absorb type C radiation. The apparatus also includes a flow meter for controlling the flow rate of the blood product to be treated.