Q. What are electromagnetic fields (EMFs) and how
will I know if they are present in my building or facility?
A. Electromagnetic fields are invisible electric and magnetic
fields created as a by-product wherever electricity (AC and DC) is utilized.
Magnetic fields can penetrate buildings and people and can be detected
when computer monitors jiggle or lose color, noise in audio-visual equipment
or data errors and loss in magnetic media.
Q. What are the most common sources of electromagnetic
fields?
A. AC sources include transformer vaults, network protectors,
secondary feeders, switch gears, busway risers, electric panels and transmission
lines. DC sources include subways, electrified trains and MRI units found
in hospitals.
Q. Are there other electromagnetic field sources that
are important to know?
A. Yes. National Electric Code (NEC) wiring violations and shorts
can inject ground currents onto metal conduits, water pipes, building
steel and HVAC ducts, which can cause electromagnetic interference (EMI)
throughout a building.
Q. Are there other RF electromagnetic field sources
outside a building that can cause RFI?
A. Yes. On many roofs and upper floors, antenna farms and microwave
dishes can generate RFI (radio frequency interference) and it could exceed
potential health and safety electromagnetic radiation (EMR) risks as
specified by the 1997 Federal Communication Committee (FCC) Office of
Engineering & Technology (OET) Bulletin 65 (Edition 97-01) -
Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency
Electromagnetic Fields. Mandated action (i.e., posting RADHAZ signs,
wearing RF personnel alert meters, completion of RF RADHAZ Safety Plan & Training,
etc.) is required by the owner/manager of the roof antennas when the
electric field strength/SAR levels exceeds the FCC OET Bulletin 65 guidelines
for maximum permissible exposure (MPE) for:
-
Occupational/Controlled environments, which applies
only to technicians, engineers, maintenance personnel trained to
work in elevated/high EMR levels; and,
-
General Population/Uncontrolled environments such as
tenant spaces, offices, apartments, hotel rooms, restaurants, and
observation decks where people are not aware of potential EMR exposure
risks.
Q. If electromagnetic fields cannot be seen, how do
you measure levels and source(s)?
A. Only a qualified EMF engineer, using state-of-the-art instrumentation,
can identify electromagnetic field sources and the varying levels throughout
a building. Clients should be provided with 3-D color graphical contour
plots depicting electromagnetic field levels throughout a room(s) or
building plus a written evaluation identifying electromagnetic field
sources, recommended mitigation solutions and the costs involved. The
written evaluation should also discuss health and electromagnetic field
exposure issues, NEC wiring violations and grounding and plumbing current
problems -- if any.
Q. What are the most common solutions to electromagnetic
field problems?
A. National Electric Code violations must be found and eliminated
(an EMF survey instrument used by a qualified engineer is the quickest
way to find shorts). The electromagnetic fields generated by shorts cannot
be shielded. As for electromagnetic fields created by plumbing currents,
a dielectric coupler will generally solve the problem. If the electromagnetic
field source or the affected people and equipment can be moved easily
(known as "prudent avoidance"), the creation of empty space (EMFs diminish
quickly over distance) could solve the problem. It is very unlikely that
productive space will be vacated permanently to solve electromagnetic
field problems. Generally, shielding is the most common solution to electromagnetic
field problems and shielding the source or shielding the room(s) and
people are the two choices. If the electromagnetic field sources are
not accessible, then shielding the room(s) or the area in which people
work with EMF sensitive equipment is selected -- the solution most often
used.
Q. What criteria should I use to evaluate an electromagnetic
field problem-solving solution?
A. Any electromagnetic field solution should include a written
guarantee of performance, i.e. the affected area(s) will not exceed 10
milligauss (the measurement for detecting EMF) at one meter above floor
level (average height of computer desks) over 95 percent of the affected
area. Generally, 10 mG is the threshold for computer interference. The
guarantee should include price, shield design, installation time, final
verification report of performance and references. No one shield design
cures all electromagnetic field problems. Each shield must be designed
to mitigate the particular EMF source(s) and levels present -- one shield
does not fit all. For example, a steelplate shield will not solve most
electromagnetic field problems.
Q. If an electromagnetic field problem is discovered
at a commercial, institutional or industrial site, can I expect financial
help from other sources?
A. Unless you have specific EMF coverage in your casualty and
property insurance, it is not likely you will get financial help from
those sources. If you rent or lease space, you can ask the owner to solve
the problem or move out. Historically, the power companies have taken
no responsibility for electromagnetic field problems. The best course
of action is to have a full spectrum EMF survey conducted before you
build, buy, rent, lease or renovate any building, area or space. If electromagnetic
field problems are discovered, make corrective action mandatory before
building or moving in. Prudent casualty and property insurance companies
as well as mortgage bankers should survey for electromagnetic fields
before offering their services.
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