Different building materials are susceptible to mold growth. The purpose of this research was to determine at which conditions molds grow and which materials present as favorable substrates. In this master thesis, we studied larch, spruce, pine sapwood, oriented strand board, and gypsum board. On building materials samples, we inoculated conidia of Penicillium expansum, Aspergillus niger, and Sydowia polyspora and incubated them at three different relative humidity levels (RH: 75 %, 85 %, 95 %) and two temperature levels (15 °C, 25 °C). Test samples were considered to have failed when the rating of a mold growth first reached 2 or higher based on the ratings in Table 3. P. expansum and A. niger grew fastest on oriented strand board and gypsum board samples. In lower relative humidities, growth was non-existent. S. polyspora grew faster on wooden samples, as well as at lower relative humidities. At 25 °C, molds achieved a rating of 2 faster or at the same time as at 15 °C in most of the conditions. The same applies to higher relative humidity. At 95 %, RH molds achieved a growth rating of 2 faster than at lower ones. All materials had been determined with critical relative humidities which show us, in which relative humidity intervals did the samples reach mold growth rating of 2. In addition, we also did a paste–test in which the aforementioned molds were inoculated on PDA medium with the addition of ground materials (50 % of added ground materials based on the medium). The influence of materials present was noticed on medium with added pine sapwood and A. niger and on medium with added larch and P. expansum.
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