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 .