Magnetic field environments at power frequency inside modern buildings

This paper presents the results of indoor ELF magnetic field environments measured for three kinds of place (home, office, and school) using various electrical devices. Both the fields emitted by devices in isolation and in composite environments were measured. For composite environments, measurements were made with a distance interval of 0.5 m in grids at heights of 0.3 m, 1 m and 1.5 m above the floor ground respectively. It was found that the magnetic field environment in a typical home is the worst and that in school classroom is the best. This is understandable as many electric appliances are used in a home, while few electric appliances are used in a classroom. For devices in isolation, the measurements were made with an interval of 0.05 m so that the field strength versus distance from the source can be found. Results show that the magnetic fields at close proximity could reach as high as 36 μT, 14 μT and 3.2 μT for the exhaust fan in kitchen, LCD TV set in living room, and desktop computer and typing machine in office, respectively. In general, the magnetic field strength decayed rapidly to less than 0.2 μT at 1 m away from the power unit of the device.