An additive manufacturing method including repeatedly applying a layer of building material on a previously selectively solidified building material layer and scanning the layer at positions corresponding to the cross-section of the object in this layer, where the laser radiation is generated by a laser light source and is directed onto the building material layer via optical components. An optics compartment is encased by an optics compartment housing and accommodates the optical components. A defined gas atmosphere is maintained inside of the optics compartment, wherein the relative humidity of the defined gas atmosphere is kept below 3%.