EMFs come from a wide range of sources and vary enormously in the strength of the fields. (This page and the links from it deal with power-frequency fields - see also static fields.)
See also: electric fields , magnetic fields , units used for EMFs, instruments available for measuring fields.
The diagram shows how the magnetic field varies over a typical house. The peaks come from the various appliances, and they are superimposed on a low background field, which varies only slightly across the house.