All the measurements were performed in the working positions at the machines. Field flux densities in the range 0–10 mT at mostly 50 Hz were found in both types of industries. Near induction heaters, both the magnetic flux density and the frequency may be very high (up to 10 kHz). Knowledge of industrial field characteristics such as frequency, flux density, and distribution will facilitate laboratory research aimed at determining possible biological effects of magnetic fields. These results indicate that biological effects of the magnetic fields probably occur (magnetophosphenes), although these phenomena are difficult to recognize in industrial localities with high background illuminatio