The Two Shielded Rooms
by Ragnar Forshufvud
Shielding, Faraday cage, grounding plane,
metal floor, shielded room, low frequency EMF, electrical sensitivity, EHS,
tall building, accommodation, case story
Before my retirement I
worked for Bofors in Sweden, a corporation which manufactures military
equipment. When computer terminals
were introduced in the offices, several employees became electrosensitive. Computer Aided Design (CAD) also caused
In 1990, two designers,
Anita and Christer, became electrohypersensitive. We tried to modify their workplace so they could continue
working there and not go on sick leave and never come back, as so many others
They were moved to an
office on the top floor of the office building. The floor was covered with a
layer of steel plates and a layer of aluminum plates, to create a shield
against the offices below. All
electrical equipment in the office was shielded and all these shields were
connected to the metal floor. The
metal floor was the grounding plane for the office. The earth itself was too far below the office.
This setup worked well
for Anita and Christer. But the
rest of their colleagues were in offices three stories below and it would be
better if they all sat closer together. Then someone thought that it should be possible to build a
shielded room on the same floor as their colleagues. The work could be done professionally by a firm specializing
in shielding. It was not unusual
for a company that produced military equipment to build a shielded room to
I was a bit skeptical
myself, as I had heard that some people who were electrically hypersensitive
did not do well in shielded rooms.
The first time I read about that was from Werner Hengstenberg in
Bavaria, Germany. Hengstenberg was
on a tear on these issues. With
the help of technical friends, he developed measuring equipment, which he sold. He did not have an academic background,
but he was electrically hypersensitive and he himself had tried to sit in a
Faraday cage, with poor result. He
naturally wondered what could be wrong with such shielded cages and he thought
there was some sort of natural radiation which humans need to feel healthy, and
it thus is wrong to shield off all radiation.
That explanation did not
impress his fellow German, Eric-W. Fischer, who had a masters degree in
engineering and taught courses about biologically compatible electrical
designs. I attended one of his
courses and heard Fischer state that it is fine to live in a Faraday cage. Another course participant took this
message to heart and built himself a Faraday cage. The shielding was metallic netting — I recall it was
netting for windows.
Unfortunately, he did not sleep well inside, as he later told me in a
So, there were some
negative experiences with metallic shielding. Before we went through the expense of building a shielded
room at Bofors, we therefore wanted to see if the most sensitive of the two
designers could even be in such a Faraday cage.
We had a small Faraday
cage we had earlier used for some experiments. It was now disassembled and in storage. We put it together and Anita sat in it
for a few days. She reported that
she did well there.
We did the test in
another building, about 40 meters (120 ft) from where we intended to build the
shielded room, but nobody thought the location was important. We just wanted to see if Anita did well
in a Faraday cage, and she did.
The project could now
move forward and the contract to build the shielded room went to a company in
Helsingborg. The company put a
disclaimer in the contract that they could not guarantee that someone with
electrical hypersensitivity would do well inside. That was a bad omen.
It didnŐt work. The two designers did not do well
inside the shielded room. They
even preferred to sit right outside it, rather than inside. They gave up after a week and moved
back to their old office on the top floor of the building.
The shielded room was
built with copper mesh, which we knew did not block low-frequency magnetic
radiation. We measured that to be
about 50 to 75 nanotesla (0.5 to 0.75 milligauss), which were common levels in
Swedish office buildings. What was
not typical was that the dominant frequency was neither the 50 hertz power
frequency, nor the 150 hertz harmonic, but 2.7 hertz. This ultra-low frequency came from a large electric oven two
floors below, that was used to make ceramic electronic components. To what extent this unusual frequency
was the cause of the problem was never investigated.
The walls of a metallic
room exposed to a low-frequency magnetic field will have induced currents with
many possible paths. This is not
the only case where such induced currents, circulating in closed loops, seem to
have made people feel unwell. Such
currents produce a magnetic field, but this field is normally weaker than the
field that induced the currents, so there is no accepted explanation why Anita
and Christer were so affected by this secondary field.
Anita and Christer
gradually recovered, and after a few years they needed no special
accommodations. It should be
mentioned that Anita had the electrical wiring in her home replaced with
shielded cables, which certainly contributed to her recovery.
Ragnar Forshufvud holds a
masters degree in electrical engineering.
He is now retired, but has retained an interest in EMF issues for people
who are electrically sensitive and published the Swedish-language book Bostad Och Halsa (Home and Health) on
this topic in 1998.