Microbial growth has been known as one of the major problems related to IAQ inresidential and commercial buildings. International and local standards define theupper limits of indoor relative humidity in order to avoid moisture related problems.However, setting limits on indoor relative humidity does not guarantee a mould-freeenvironment.
Japanese Building Maintenance Law defines that indoor humidity shall be maintained not lower than40%. But it is sometime very difficult to comply with the law. Indoor air humidifies in office buildingsmostly below 40% especially in wintertime. A request to deregulate the provision arises from HVACindustries. But a question concerning risk to deregulate the lower limit of humidity is arising.According to researches in 1960s, activity levels of influenza virus become higher when indoorrelative humidity becomes lower than 40%.
The aim was to study changes of symptoms and signs in an office exposed to flooding fromheavy rain. All 18 workers participated in medical investigations in January 1998. Thesubjects were first investigated on a Monday in a reference building and then all moved backand were reinvestigated in a damp building after 2 days of exposure.
A questionnaire on e.g. building characteristics including dampness, and allergic symptomsamong children from 8 918 homes was carried out in the year 2000. 18-24 months later, 6professional inspectors visited 390 of the homes and made inspections and measurements.Questionnaire reports on building characteristics, type of ventilation system, and buildingmaterials were in good agreement with observations from the inspectors (K=0.68-0.87). Individualkappa-values for the inspectors varied in the range of 0.33-0.96.
In order to identify the effects of various kinds of floor materials and that of humidity on theconcentration of mite allergens in houses of allergy patients, measurements were carried outin two houses near Tokyo in August, November and December 2001. Temperature, humidityand mite allergens, Der p 1, Der f 1 and Der 2, were measured and a questionnaire survey wasconducted.
Thirty classrooms in 10 schools in Shanghai, China, were investigated in winter. Dust wascollected by vacuum cleaning, analysed for ergosterol, muramic acid, and 3-hydroxy fattyacids (LPS) by tandem mass spectrometry (GC-MSMS). Airborne microoganisms weresampled on Nucleopore filters (CAMNEA). The compound 1-octen-3-ol was found in higherconcentrations in indoor than in outdoor air. Total indoor bacteria were positively correlatedto both LPS and muramic acid in settled dust. Indoor and outdoor air contained many viablespecies.
During the research, air samples were taken by exposure of agar plates and taking smearsamples from the AC equipment. Sampling took place during the autumn because theconcentration of spores at that time reaches its peak.
In two school buildings, concentrations of viable fungal spores in air, material and insurface samples were high indicating moisture and mould damages. Microbesincluded numerous moisture indicating species (e.g. Aspergillus versicolor,Trichoderma, Fusarium, Stachybotrys, Chaetomium, Streptomyces). After renovation,the school buildings were thoroughly cleaned. Surfaces still had abundant anddiversiform microflora. After repeated cleaning, abundance and diversity ofmicroflora diminished.
Moisture-related indicators indoors are, e.g. visible mould and damp spots, condensation onthe inside of window panes, detached floor covering materials, flooding and bad odours. Suchindicators are frequently found and are reported to appear in 25-80% of the buildingsworldwide (Bornehag et al., 2001). Dampness has also been identified as a major risk factorfor, e.g. respiratory symptoms such as asthma, cough and wheezing among both children andadults (Bornehag et al., 2001).
The aim of the study was to find out if the location of material has effect onmicrobiological findings. Material samples (n = 735) were taken from the buildingswith susceptible moisture damages. Viable fungal spores and bacteria were analysedfrom paperboard, insulation material and wood samples from inner and outer parts ofconstruction. Microbial biodiversity was largest in inner parts of construction. In wallcavity, insulation material had largest microbial diversity.
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