Boron compounds are effective biocides in rather low concentrations. Boron is considered as environmentally friendly preservative. However, its key disadvantage is, that they can be leached from wood in wet conditions. Therefore, boron fixation was improved with quaternary ammonium compounds and ethanolamine. Our aim was to determine the minimum inhibitory concentration of different combinations of active ingredients: boric acid, ethanolamine, quaternary ammonium compounds, and a mixture of all three preparations (EABQ) against mold and blue%stain fungi. Performance of respective aqueous solutions was determined according to EN 152-1 (1996) standard. Laboratory samples were made of Scots pine sapwood in prescribed dimensions and shape. On the other hand, field test samples were prepared from fresh spruce wood. The results clearly indicates, that the efficacy of the products increases along with thin creasing concentration of active ingredients in the solution. The test was also carried out in the field test site, in order to elucidate the problem of staining fungi during timber shipping and storage. As expected, the results of field and laboratory tests differed due to environmental factors on the field.
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