Microbial Growth and Secondary Emissions – Their Main Causes in Swedish Problem Buildings T. Hall 1,3 , B. Wessén 2 and Lars-Olof Nilsson 3 1 Chalmers University of Technology, Department of Building Technology, SE-412 96 Göteborg, Sweden email: torbjorn.hall@bt.chalmers.se, http://www.bm.chalmers.se/indexe.htm 2 Pegasus Laboratory Ltd, Box 97, SE-751 03 Uppsala, Sweden 3 Lund Institute of Technology, Div. of Building Materials, P O Box 118, SE-221 00 Lund, Sweden Summary: In Scandinavian buildings, moisture related problems are a dominating factor in explaining “sick buildings”. This study comprised 113 Swedish cases during the period 1993 to 2002. The occupants had pronounced health complaints and/or suffered due to abnormal odours. The results showed that in 92 % of the cases, the problems were mainly caused by emission sources due to different kinds of harmful moisture. The remediation strategy resulted in an improved health situation as well as removal of abnormal odours. Keywords: Micro organisms, Secondary emissions, Moisture damage, Investigation Category: Case studies 1 Introduction In Scandinavia it has been amply demonstrated that some types of construction sustain mould growth while in others abnormal chemical emissions also occur. Both types of damage are due to harmful moisture. It is also well known that occupants sometimes have pronounced health problems associated with living or working in damp buildings. In contrast, outside the group of professional investigators, there is a lack of knowledge as to which components are damaged and how often this occurs. These professional investigators have also learned by experience that when a well performed investigation has identified new or old moisture damage, followed by a well performed remediation process, the result is almost always significant improvement in the health situation and also removal of abnormal odours. The causality between bad health and measurable pollutants in the indoor environment is largely unclear. Investigators are therefore trying, without a scientific foundation, to solve problems in buildings where the occupants complain of SBS. This is unsatisfactory and has also resulted in scepticism on the part of scientists, allergists and others about the approach employed by the investigators to solve these problems. It is also important for the whole building sector to learn from earlier mistakes that had caused damage and a deterioration in indoor air quality. This will help the remediation processes and help avoid the same mistakes in the future. One way to improve knowledge about these and to help sectors outside the professional investigators to better understand the situation is to describe examples and the results of indoor air investigations in buildings with SBS. 2 Aim The aim of this work has been to compile and to disseminate the experiences of professional investigators concerning damage in buildings which have given rise to indoor environment related problems. 3 Methods Written documentation relating to about 300 commissions carried out by a firm of consultants in Central Sweden during the period 1993 – 2002 has been studied. The clients, who were mainly the owners of the buildings to which the commission referred, represent a mixture of property firms of different sizes, municipal and national authorities and private owners of single family houses. The common factor leading to the engagement of the firm of consultants was that the problems encountered needed expert assistance for their solution. Only indoor environment investigations relating to problems due to abnormal odours or problems where the occupants referred to some form of complaint/ symptom due to living or working in the building were chosen for the study. Damage investigations concerning the causes of faults such as visible damage were not included. The methods used to characterise the SBS depended upon the number of occupants. In larger buildings, with more than 20 occupants, in most cases a standardised questionnaire was used to assess the scope of complaints before and after the remedial measures. The MM Questionnaires [1] developed at Department of Occupational and Environmental Medicine, Örebro University Hospital were used in this case. The occupants in the building answered how they had perceived the environment and if they had health