Low-frequency electromagnetic fields and their effect on the employee are paid minimal attention. In this work will measure and describe the influence of low-frequency. Our experiments show necessity of controlling the frequency not only in devices but also on their power supply and cables. All measures were made on VEMA-041 measure equipment with computer software. Measurements were made with the respect to various aspects. From the measured gas welding unit the cable acts as the antenna with characteristic frequencies of 100 Hz and its harmonics. Due to this knowledge we can increase production efficiency of the employee and also their health will improve.