IAQ Simulator Tests: VOC Emissions from Hidden Mould Growth

Clean indoor air is a prerequisite for the welfare of the society. The Indoor Air Quality simulator (IAQ simulator) offers a research tool for building physic and building material research to evaluate the effect of the complicated causal connections of indoor air quality and multilayer building structures, materials and their unexpected exposure to moisture and microbial growth. In Microdiverbuild-project, the IAQ simulator was used to assess the drift of microbial metabolites (e.g. volatile metabolites of micro-organisms, MVOC) from a moisture damaged wall structure into indoor environment under various material moisture loads and pressure differences over the structure. Even low under-pressure has been found to cause infiltration of impurities in the indoor environment but unnecessary high under-pressure indoors increases further concentrations of impurities from the building structures. Also, infiltration of microbial gaseous contaminants from active mould growth inside the structure decreases indoor air quality. The wood laths were covered by active mould growth, and represented a mould damaged wall structure (mould index 4-5). These laths were assembled inside the wall and simulated a hidden active mould growth having air leakage routes through the envelope. Two pressure difference levels simulated normal (low pressure difference) and unbalanced ventilation when pressure difference may increase as high as -20 Pa.The simulation test showed clearly MVOCs indicating hidden microbial growth. In our previous study, VOC profiles were developed based on building occupants complaints about poor IAQ, and found high ketone concentrations indicate mould problem which is equal with results of this study. However, it is known that MVOCs can be released from other sources in real buildings and the impact of relative humidity of the material is remarkable.