The application of LED technologies in the industry is gaining more and more popularity. In case of reconstruction or new construction of an industrial building, it is envisaged that the lighting will be built with LED luminaires. A disadvantage is the use of electronic starting and regulating devices (LED Drivers), which generate high harmonics and thus pollute the electrical power network. The report presents a long-term study of the harmonic pollutions, generated by LED lighting in a medium brewery industrial building. The study was conducted for 2 months, under different modes of operation of the LED lighting system. The obtained data are summarized and systematized. The report presents the summarized results of the study in tabular and graphical form. It was found that the harmonic pollution resulting from the lighting system exceeds the requirements of the electricity quality standard. Conclusions and some recommendations from the research are formulated.