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The prevention of decrease of quality caused by microbial activity in footwear materials entails the use of biocides. However, these substances may pose a hazard to humans and to the natural environment. The paper presents the results of antimicrobial effect investigation for cowhide leather treated with oregano oil. In these studies oil was applied by spraying onto the finished leather surface and examined to determine its antimicrobial activity by using the Agar Diffusion Plate Test. These results were compared with those where a cowhide leather was treated with oil at the stage of fatliquoring. In addition, the oregano oil toxicity level was assessed and compared with biocides used in the tanning industry. Introducing oregano oil into the leather at the stage of fatliquoring provides a better antimicrobial effect than by spraying, however hygienic finishing of leather can be obtained by introducing oil into the raw material by these both methods. The oregano oil is characterised by the lowest number of hazards and toxicity as compared with commercial biocides. The use of essential oils as natural biocides in the tanning industry seems to be especially important and suitable solution considering the harmful effects of synthetic biocides to humans and the environment.

Abstract. in the paper the authors examined the relations between the physical deterioration degree and the price of the tenement-houses in Wrocław. The researches concern the year's 1991-2009. According to the following analyses: technical, technical-economic (concerning the relations between buildings technical condition and buildings price) and economic the authors have come the conclusions concerning the sensibility of the revitalization work. The authors also estimated the purchase limit profitability of the tenement-houses, which are going to be repaired and modernized or to be demolished and next to be built a new tenement-house. The direction of the engineering activities was shown. They could improve the economic effectiveness of the revitalized tenement-houses.Keywords: revitalization of apartment buildings, building development of Wrocław in the beginning of the XX century, physical deterioration degree of buildings, economic effectiveness of revitalization.

When a decision is taken about assembling an overcladding system on building external walls, an expected profit is calculated according to the economic discounting formulae. However, these formulae do not take into account the unplanned repair costs. The unplanned repairs have to be done to remove the defects which appear on a building wall overcladding during its service life. In order to do that the authors have performed the expert's surveys of technical condition of the existing overcladdings. These overcladdings were assembled on the external walls of 497 apartment buildings located in Wrocław (Poland) in 1990.2000. The qualitative results of technical condition expert's surveys, their transformation into the quantitative values done according to the elaborated model and estimation of the risk related to the expected profit decrease are presented in the article.

The hygienic properties of lining leathers can be improved significantly by introducing oregano essential oil into leathers. This is because adding antiseptic oil makes leathers more resistant to microorganisms that are potentially harmful to humans and cause damage to animal leathers. The paper presents the results of tests to check selected mechanical properties -tensile strength, elongation and tear load -of leathers fatliquored with oregano essential oil at a concentration of 3% w/w and without this treatment.The tests were carried out on the Instron 5544 testing machine.The leathers enriched with oil met the standard requirements set for lining leathers for of the parameters: tensile strength and elongation. Statistical analysis using the chi-squared, Hartley and Fisher-Snedecor tests at an assumed significance level of α = 0.05 revealed that leather enriched with oregano essential oil has a significantly higher tensile strength than leather fatliquored without this oil, while both leather samples Elżbieta Bielak, Cracow University of Economics, Faculty of Commodity Science and Product Management, Department of Industrial Commodity Science, Rakowicka 27, 31-510 Kraków, e-mail: bielake@uek.krakow.pl Ewa Marcinkowska, Cracow University of Economics, Faculty of Commodity Science and Product Management, Department of Industrial Commodity Science, Rakowicka 27, 31-510 Kraków, e-mail: etmarcin@cyf-kr.edu.pl * This paper presents the results of a research project co-financed from Ministry of Science and Higher Education funds granted to the Faculty of Commodity Science at the Cracow University of Economics for research projects implemented by young scientists and doctoral research fellows and for maintaining research potential. Elżbieta Bielak, Ewa Marcinkowska 20showed no significant difference in elongation and tear load. Thus, it can be concluded that adding 3% w/w of oil will have not have an adverse effect on basic mechanical properties of leathers.