EMFs are invisible lines of force that exist in the area surrounding any electrical device.
They are measured in gauss or tesla and are not easily shielded or weakened by most material. EMFs are reduced in strength with increasing distance from the source. In general, the higher the frequency, the greater the amount of energy in the field. Electric fields close to transmission lines are much stronger than the fields found near electrical appliances, but they are reduced in strength by objects such as buildings, trees, and vehicles. Magnetic fields very close to electrical appliances are often stronger than the fields directly beneath power lines, but they decrease in strength with distance more quickly than do power-line fields.