VOLATILE COMPOUNDS ORIGINATING FROM MIXED MICROBIAL CULTURES ON BUILDING-MATERIALS UNDER VARIOUS HUMIDITY CONDITIONS

We examined growth of mixed microbial cultures (13 fungal species and one actinomycete species) and production of volatile compounds (VOCs) in typical building materials in outside walls, separating walls, and bathroom floors at various relative humidities (RHs) of air. Air sampl es from incubation chambers were adsorbed on Tenax TA and dinitropheny lhydrazine cartridges and were analyzed by thermal desorption-gas chro matography and high-performance liquid chromatography, respectively, M etabolic activity was measured by determining CO2 production, and micr obial concentrations were determined by a dilution plate method. At 80 to 82% RH, CO2 production did not indicate that microbial activity oc curred, and only 10% of the spores germinated, while slight increases in the concentrations of some VOCs were detected. All of the parameter s showed that microbial activity occurred at 90 to 99% RH. The microbi ological analyses revealed weak microbial growth even under drying con ditions (32 to 33% RFI), The main VOCs produced on the building materi als studied were 3-methyl-1-butanol, 1-pentanol, 1-hexanol, and 1-octe n-3-ol. In some cases fungal growth decreased aldehyde emissions. We f ound that various VOCs accompany microbial activity but that no single VOC is a reliable indicator of biocontamination in building materials .