University of Washington University of Washington
Facilities Services Safety
Facilities Services
TIPS TO REDUCE ELECTRICAL
IEC CATEGORY SPECIFICATIONS FOR HAZARDS:
Frequently inspect your workplace for
ELECTRICAL TEST EQUIPMENT
damaged, overheating, or misused
Higher categories are closer to the power
electrical equipment (appliances, tools,
source.
cords, outlets, wiring, light switches,
light sockets etc) and report any
CAT IV- Three-phase at utility connection, any
problems to your supervisor.
outdoor conductors. Refers to the “origin of
installation”; where a low-voltage connection is Only have qualified, authorized
Electrical Hazards
made to utility power. Includes electricity employees work on electrical
meters, primary overcurrent protection equipment and systems.
equipment, outside and service entrance, Follow safe work practices and wear all
service drop from pole to building, run between the required personal protective
meter and panel, overhead line to detached equipment when working on or near
building, underground line to well pump electrical equipment.
CAT III - Three-phase distribution, includes Work on de-energized circuits unless a
single-phase commercial lighting. Refers to shut-down is not feasible.
equipment in fixed installations such as Store flammable materials away from
switchgear, polyphase motors, bus and feeders electrical sources.
in industrial plants, feeders and short branch Follow the recommendations in the
circuits, distribution panel devices, lighting Ground Fault Circuit Interrupters and
Extension Cords brochures.
systems in larger buildings, and appliance
outlets with short connections to service Know the maximum voltage you will be
testing.
entrance.
Use electrical test equipment with the
CAT II - Single-phase receptacle connected proper IEC category rating for the work
loads. Refers to appliances, portable tools, being done.
other household and similar loads, outlet and Keep area 36” in front of electrical
long branch circuits, outlets at more than 10 panels clear of ALL materials.
meters (30 feet) from CAT III sources, and
outlets more that 20 meters (60 feet) from CAT “Better a thousand times
IV sources. careful than once dead”
CAT I – Electronic. Refers to protected -Proverb
electronic equipment, equipment connected to
(source) circuits in which measures have been
taken to limit transient overvoltages to an
appropriately low level, any high-voltage, low-
energy source derived from a highwinding DEVELOPED BY THE MAINTENANCE & ALTERATIONS
AND CAMPUS ENGINEERING & OPERATIONS DIVISIONS
resistance transformer, such as the high- OF FACILITIES SERVICES
voltage section of a copier.
10/05
Electrical Hazards 4. EXPLOSIONS Explosions occur when
We use electricity everyday without giving electricity ignites an explosive mixture in the
much thought to the hazards it can present. atmosphere. Explosive atmospheres result
The following information will explain the from the accumulation of flammable vapors or
hazards of electricity and how to reduce or gases from nearby sources and processes.
eliminate exposure to electrical hazards. Ignition sources can be overheated conductors
or equipment, or normal arcing (sparking) at
HAZARDS OF ELECTRICITY switch contacts.
The five primary hazards associated with
electricity and its use are;
1. SHOCK Some common causes of electrical
shock are contact with bare wire, unsafe 3. ARC-FLASH Arc-flashes occur from high-
equipment, inadequate grounding, damp floors, amperage currents arcing through air. An arc-
water, metal ladders, power still on, and blast happens when there is contact between
lightning strikes. The effects, or damage, two energized points. This contact can be 5. FIRES Electricity is often the cause of fire
produced by an electrical shock depend on the caused by people, or equipment failure. The both in the home and workplace. Defective or
duration, quantity, frequency, and path of the primary hazards associated with an arc-flash misused electrical equipment, such as old or
current passing through the body, and the are: defective power strips, is a major cause of
skin’s moisture content.
Thermal Radiation. The radiated thermal energy, electrical fires. High resistance connections are
or heat, can cause burns. Proper clothing, work one of the primary sources of ignition. High
Your nervous system is an electrical network
distances, and overcurrent protection can resistance connections occur where wires are
that uses extremely low amperage currents. An
reduce the chances of receiving incurable improperly spliced or connected to other
electric shock--with even very low current--can
burns. components such as receptacle outlets and
disrupt normal functioning of muscles--most
Pressure Wave. A high- energy arc fault can switches.
significantly, your heart. It may cause the heart
to lose its coordination or rhythm. Shock produce a considerable pressure wave (a SELECTING ELECTRICAL TEST
causes muscle contractions that can cause a person 2 feet from a 25,000 amp arc would
experience a force of about 480 lbs). Such a EQUIPMENT
person working from a ladder to fall, or can
cause the person receiving the shock to be pressure wave can cause ear damage, Selection of properly rated electrical test
unable to "let go”. These effects can be caused memory loss (mild concussion); and may throw equipment can mean the difference between
by currents that produce no noticeable heating the victim away from the arc-blast. This would completing a job safely, or sustaining serious
of tissue or visible injury. reduce the exposure to the thermal energy, but injuries. The International Electrotechnical
increase the risk of serious physical injury. Commission(IEC) has developed specifications
2. BURNS Although a current may not pass to help determine which category of test
Projectiles. An arc-pressure wave can propel big
through vital organs or nerve centers, internal equipment is needed for a task. The electrical
electrical burns can still occur. objects over a considerable distance.
A high-energy arc can cause metal test equipment, and attachments, used for the
equipment components to become molten, work must be rated for that category, or higher.
These burns are the result of heat generated
then these droplets of molten metal can The category rating (CAT) for electrical test
by the current flowing in tissue, and can be
be thrown through the air, causing burns or equipment can be determined by looking for a
either at the skin surface, in deeper tissue
igniting clothing up to 10 feet away. label on the equipment, or by reading the
layers (muscles, bones, etc.), or both. These
types of electrical burns heal slowly. equipment manual. If there is no IEC category
rating for the test equipment, it should not be
used.