An atomic layer deposition apparatus, having a first series of high pressure gas injection openings and a first series of exhaust openings that are positioned such that they together create a first high pressure/suction zone within each purge gas zone, wherein each first high pressure/suction zone extends over substantially the entire width of the process tunnel and wherein the distribution of the gas injection openings that are connected to the second purge gas source and the distribution of the gas exhaust openings within the first high pressure/suction zone, as well as the pressure of the second purge gas source and the pressure at the gas exhaust openings are such that the average pressure within the first high pressure/suction zone deviates less than 30% from a reference pressure which is defined by the average pressure within process tunnel when no substrate is present.