These are unavoidable, caused by current-carrying devices including transformers, electric service panels and conduit. With today's increasingly sensitive technology, even relatively low background fields may be sufficient to cause equipment interference. Problems with magnetic fields frequently emerge immediately after a new tenant moves in or after a build out or renovation. Space that was either previously unused, or not used for sensitive equipment operations may suddenly develop a problem. For example, a fairly low tech tenant may move out and a high tech graphics art group may move in.
New problems are also common when there is a change in the building's power structure.
Proper planning during a renovation or lease negotiation can save considerable time and money if there is a potential EMF problem.