Abstract: Method of replacing a PCB-containing coolant in electrical induction apparatus having a vessel containing said PCB-containing coolant, an electrical winding and porous solid cellulosic electrical insulation immersed in, and impregnated with, said PCB-containing coolant with a substantially PCB-free high boiling dielectric permanent coolant into which any residual PCBs elute at no greater than a selected target rate comprising steps of (a) draining the PCB-containing coolant from the vessel, (b) filling the vessel with an interim dielectric coolant, (c) electrically operating the apparatus, (d) removing interim coolant containing eluted PCB, (e) repeating steps (b), (c) and (d) a sufficient number of times until the PCB elution rate does not exceed 5 times a selected target rate, (f) filling the vessel with PCB-free high boiling dielectric silicone oil as coolant, (g) electrically operating the apparatus, (h) thereafter removing the silicone oil coolant containing eluted PCB, (i) repeating steps (f), (g) and (