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. The method includes providing an electrospinning apparatus and simultaneously electrospinning at least one solution onto a first surface and an opposing second surface. The diffuser assembly also may include an exhaust flow path defined between the outer boundary member and the inner boundary member.