A release agent, in particular silicon oil, is applied to the surface of a fuser roller of a digital printer using dry toner to reduce contamination. Contamination of the surfaces is reduced or even prevented when the separating agent is diluted with a solvent having a boiling point in the range 60°C to 160°C.As the temperature of the fuser roller is significantly above the boiling point of the solvent it evaporates immediately after application resulting in a thin and smooth layer of fuser oil on the fuser rollers.Due the viscosity reduction by the addition of solvent, silicone oil with higher viscosity can be used and can be diluted by the solvent to the viscosity necessary for application. Thus the viscosity of the oil applied to the roller is higher after evaporation of the solvent compared to application of lower viscosity oil without dilution. That reduces volatilization of the oil off the roller that may cause oil pollution of other parts of the printer.The solvents reduce the viscosity of the oil that much that it maybe applied to the fuser roller point wise by e.g. an ink jet application device. The image data allow controlling the quantity of oil depending on the amount of toner.The evaporated solvent has to be removed from the exhaust air of printer by suitable filtering means before the air leaves the printer. Beside the solvent, ozone from the corona charger in the electrophotographic process has to be removed. This can be done in a special environment by first reaction the evaporated solvent - preferably a halogen containing solvent - with the ozone and then extracting the reaction product from the exhaust air by suitable filter e.g. charcoal filter.