A specific supply of fresh air does not only alleviate the harmful substances in the bedroom to a certain degree. It is also necessary, because with every breath we take, we transform the oxygen in the air into carbon dioxide. It is impossible to sleep in such bad air. Furthermore, fresh air regulates the humidity, which should ideally be between 40 and 60 %. This is why you should air your bedroom well before going to bed and then close the window again, especially in winter, as cold air cannot absorb the moisture we release during the night. The moisture is absorbed by the mattress instead, which can lead to the build up of mould.

If a bedroom is thoroughly aired in the morning and in the evenign, most of these problems can be avoided. Windows should be opened wide and draughty conditions be provided, even on a rainy day and in winter. If it is cold outside, a few minutes are already sufficient, as the air exchange is accelerated by the greater temperature difference between inside and outside.