On 6 January 1998 VitaTech was
contracted by a Washington, DC company to design, install and test
an extremely low frequency (ELF) magnetic shield in a lower level area.
The emf sources were a secondary feeder and transformer vault beneath
the sidewalk adjacent to the building and from a switchgear room under
the east transformer vault.
In December 1997, a before shield ELF EMF survey was
performed in the lower level rooms of the building. The 1-meter height
levels ranged from 10 mG to 86 mG along the 66-foot south wall . Secondary
feeder emissions are the dominant emission source in office-4 and the
southwest corner of office-3. A complex emission profile was produced
by the transformer and secondary feeders from the southwest corner
of office-3 to the east wall. The same problem occured in Room B-103
at the southeast corner from the secondary feeders and along the south
wall from the combined transformer and secondary feeder emissions.
Estimated summer magnetic emission levels are probably between 30-258
mG, if not higher, along the 66-foot south wall in rooms B102 and B103.
In the middle of January 1998, the dual-substrate
2,300 square-foot AC ELF magnetic shield was installed over the secondary
feeder and transformer vault walls/floors. The shield required 4 days
of installation by our shielding crew. Six layers of shielding materials
were installed on the walls and five layers on the floor. The shield
installation work was completed without any major problems. The shield
was in compliance with the 10-mG magnetic flux density requirement
measured 1-meter above the floor over 95% of the shielded office areas.
Project Data
 Video
Magnetic Shield Images
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