Personnel in Call Centers around the world report
being shocked as they perform their jobs. The
shocks typically are to the head area near the headsets they wear.
Where else but call centers would one find several hundred people
in an office environment tethered to a grounded telephone system
by headsets? The phenomena are real and so are the effects on
The reported problems due to these shocks range
from mild annoyance to loss of sight and hearing. Luckily the
more drastic affects seem to be temporary.These are electrostatic
shocks primarily of the person to the phone system. Typically
the electrical or telecommunication systems are not to blame as
the source of the electrostatic voltages which result in the painful
Sometimes the source may be atmospheric in nature.
Lightning in the general area may cause what experts call a "ground
plane rise" and give a shock to persons wearing headsets.
However, this is a more rare phenomenon if the system has proper
surge protection. In this article I am addressing only the shocks
caused by electrostatic charges accumulated on the personnel and
discharged to other persons, the equipment or through the headsets.
The primary causes
of the electrostatic charge are personnel actions and clothing
in relationship with the call center floors and chairs. In
other words, the personnel themselves charge up their bodies because
they wear clothes and shoes, which generate electrostatic charges
when they scoot in and stand up from their chairs and when they
walk on the floors. When this charge reaches enough potential
(voltage) on the person to jump the gap between their ear and
the headset, a shock occurs. Most headsets have some sort of insulative
piece that cushions the ear to the headset speaker. The distance
of this will hold off and arc of approximately 20,000 to 35,000
volts on the person. This means that by the time the electrostatic
potential is great enough to jump, it is sufficient to cause physical
pain. Most call centers have normal
office style chairs, which have no antistatic capabilities. Also
most call centers have normal carpeted floors with carpet that
has little ability to keep static charges down against many shoe
When a carpet
is sold as "antistatic", it means that it has been tested
at 20% RH against a standard Neolite sole sandal and found to
be below 3,000 volts. This does not guarantee that the voltages
on a person at any other humidity or wearing any other shoe will
be less than 3,000 volts. In fact many shoes tested against "antistatic"
carpets have much higher results. Most people can not feel below
3,500 volts when they discharge from their fingers such as getting
out of a car or walking across a carpeted floor and touching a
doorknob. However, when such a discharge is allowed to occur at
the ear lobe area, the sensitivity is much greater.
carpet from an antistatic point of view is needed when personnel
are wearing telephone headsets. The application of antistatic
chemicals to standard "antistatic" carpet will keep
personnel voltages down but it is a temporary fix that must be
reapplied every few months.
The best carpet for the
reduction of charges is conductive.
This means that the carpet is made with
conductive fibers allowing it to discharge static charges from
the shoes of personnel. Companies such as Static
Smart Environments manufacture such carpets in a wide
range of styles and colors. Our labs have tested Static
Smart carpets in very low humidities with insulative shoes
and found that they provide a very low static generation for call
Personnel add considerably to their
electrostatic charging by the shoes they wear. Leather soled shoes
are usually better than shoes with rubber soles. However, when
conductive carpet is used with conductive footwear such as heel
grounders or ESD shoes, the voltage on a person is kept below
100 volts. ESD Shoes may be acquired from Iron Age shoes. Conductive
heel grounders may be obtained from several sources such as
3M and DESCO.
When most normal shoes are worn, conductive carpets generally
keep the voltage on personnel below 1,500 volts which is well
below the perception of pain during a discharge.
Normal office style chairs have polyester
upholstery and have no means of grounding the chair. In
the electronics industry where computer chips may be sensitive
to a few volts, the chairs are conductive and have grounding mechanisms.
In normal office chairs, when a person sits in and scoots around
in the chair then stands up, they accumulate a significant electrostatic
charge which may then discharge through the telephone headset
or to another worker. If that other worker just stood up from
their chair and walked over on non-conductive carpeting, the potential
difference or the total voltage between the two people may double
because the voltages may add. In this case the shock would also
be doubled in intensity and also may cause two people discomfort.
In call centers conductive chairs should be used. These chairs
are usually very expensive and by the time the problem is known
the call center usually has already purchased several hundred
alternative to buying a conductive chair is to use a conductive
cover, which has conductive threads woven into it. These covers
are available through DESCO
in Miami, Florida. Patlon has filed a patent disclosure on
this innovative system which may eliminate static shocks for all
office works including those in call centers. Our lab tested
Desco's conductive covers and
found that they keep the voltages on persons below about 1/5th
that of the plain chair.
Of course the clothes that a person
wears are very important to how much electrostatic charges are
generated by the person. Oddly enough, cotton clothes, which are
normally very good from an electrostatic point of view, may charge
more against a polyester upholstered chair than blended fabrics.
One method of keeping the voltage due to clothing on a person
down is to require the personnel to wear conductive lab coats.
This in combination with the chairs would disallow the kind of
potentials now experienced in the call centers. Several companies
provide conductive lab coats for use in office environments.
Every call center has a unique situation
for electrostatic problems. A survey of the needs should be performed
prior to any actions. However, if all the main variables are controlled:
Chairs, Floor, Clothes and Shoes
problem should go away painlessly.
Please give us your comments
For further information contact Steve Fowler at
Fowler Associates, Inc.
We have solutions ready to use