The invention concerns a method of adjusting a room air in a first room wherein the room air is supplemented continuously or at recurring intervals of time by nitrogen or a nitrogen-bearing, carbon dioxide-poor gas mixture in such a way that the proportion of oxygen in the room air is less than 20.9% by volume and the proportion of carbon dioxide in the room air is less than 1% by volume, wherein at the same time at least a slight overpressure in relation to an outside atmosphere surrounding the room is set in the room.