The Fungal to Allergen Index is a new concept aiming at giving better information of the Indoor Air Quality. Parallel air samples are analysed for total fungi and total allergens. This gives information of the potential exposure to fungi and allergens but also an indication of the risk of a mould source. Investigations of “non-problem buildings” having no apparent moisture or mould problems, and a few buildings with mould/moisture problems showed that the median value was 8.5 % in non-problem buildings and all values was above 56% in buildings with mould/moisture problems.