Just like in many other countries after the oil crisis in 1972 Danish houses were tightened with the result that the relative air humidity rose considerably. The Ministry of Energy also demanded a lowering of the indoor temperature from 25°C to 20°C with the result that the relative air humidity rose even more. According to the latest survey 10% of Danish buildings are infected with moulds. Moulds occur in the indoor environment e.g. when humid air condensates on cold outer walls or in connection with water damage which is insufficiently dried out. In our analyses we always try to determine moulds both to genus and species. During our surveys in August 2001 and February 2002 we found 50 different species of moulds in Danish houses.
The species Penicillium chrysogenum was dominating in both spring and autumn. Aspergillus versicolor was also present in spring and autumn but in smaller numbers. Cladosporium herbarum was most common during autumn. Stachybotrys chartarum was rather rare, maybe because it is closely connected to gypsum boards. It is very important to identify the moulds to species which is shown by the following case study.
In a house where the sewer had been punctured in connection with establishment of district heating, 150 cubic metres of water had poured into the crawl space. We were called in by the occupant because she felt ill and there was a strong mouldy smell. We immediately asked her to move, with the result that her health improved almost instantly. She was so sensible that even the delivery of mail in her mailbox made her ill. A blood-test showed that she was sensitised to Trichoderma viride and Penicillium chrysogenum. The latter was found in large amounts in her house. We know that it is now possible to repair the house so that non-sensitised persons will be able to live there, but not the former occupant who will react to even small traces of allergen which are still there.
After the repair we have different methods of quality control. It is now evident that some remedies and methods will kill the spores others the mycelium and yet others both. Some methods have a lasting effect, others do not. Our methods of quality control are either contact-samples with Petri dishes where mould colonies are counted and identified to species or a test for ATP or the Mycometer-test where the enzyme β-N-acetylhexosaminidase specific to fungi is measured. The Petri dish method measures the number of living spores, while the two other methods measure the amount of mycelium. However it seems that ATP in the mycelium is broken down faster than the enzyme measured by the Mycometer-test. Therefore it becomes difficult to decide whether the mycelium is living, partly dead or completely dead, when the repair work is going to be approved.