EMF Spot Measurements
The data summarized in this table came from various sources, all of which are listed in the References section.
Industry and Sources ELF magnetic fields
measured in mG
Comments Other
frequencies
Mechanical equipment used in manufacturing
Electric resistance heater 6000 - 14,000 Tool exposures measured at
operator's chest
VLF
Induction heater 10 - 460 High VLF
Hand-held grinder 3000
Grinder 110
Lathe, drill press, etc. 1 - 4
Electro-galvanizing
Rectification room 2000 - 4600 Rectified DC current (with an
ELF ripple) galvanizes metal parts
High static fields
Outdoor electric line
 and substation
100 - 1700
Aluminum refining
Aluminum pot rooms 3.4 - 30 Highly-rectified DC current (with an
ELF ripple) refines aluminum
Very high static field
Rectification room 300 - 3300 High static field
Steel foundry
Ladle refinery
 ladle electrodes active
170 - 1300 Highest ELF field was at the
chair of control room operator
High ULF from the ladle's
big magnetic stirrer
 electrodes inactive 0.6 - 3.7
Electro-galvanizing unit 2 - 1100 High VLF
Television broadcasting
Video cameras
 (studio and minocam)
7.2 - 24 Measured 1 ft. away VLF
Vidio tape degaussers 160 - 3300
Light control centers 10 - 300 Walk-through survery
Studio and newsrooms 2 - 5
Telecommunications
Relay switching racks 1.5 - 32 Measured 2 in. - 3 in. from relays Static fields and
ULF-ELF transients
Switching rooms (relay &
 electronic switches
0.1 - 1300 Walk-through survey Static fields and
ULF-ELF transients
Under ground phone vault 3 - 5 Walk-through survey
Hospitals
Intensive care unit 0.1 - 220 Measured at nurse's chest VLF
Post-anesthesia care unit 0.1 - 24 VLF
Magnetic resonance
 imaging (MRI)
0.5 - 280 Measured at technician's
work locations
Very high static field,
VLF and RF
Government offices
Desk work locations 0.1 - 7 Peaks due to laser printers  
Desks near power center 18 - 50
Power cables in floor 15 - 170
Computer center 0.4 - 6.6
Can opener 3000 Appliance fields measured
6 in. away
Desktop cooling fan 1000
Other office appliances 10 - 200
Building power supplies 25 - 1800
Information about the magnitude of other frequencies measured can be found in the original reports from which data for this table were drawn. They are listed in the References section.