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Electrical Safety
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Electricity - The Dangers
• About 5 workers are
electrocuted every week
• Causes 12% of young
worker workplace deaths
• Takes very little
electricity to cause harm
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Electrical Terms
• Current -- electrical movement (measured in amps)
• Circuit -- complete path of the current.
Includes electricity source, a conductor, and the output
device or load (such as a lamp, tool, or heater)
• Resistance -- restriction to electrical flow
• Conductors – substances, like metals, with little
resistance to electricity that allow electricity to flow
• Grounding – a conductive connection to the earth
which acts as a protective measure
• Insulators -- substances with high resistance to
electricity like glass, porcelain, plastic, and dry wood
that prevent electricity from getting to unwanted areas
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Electrical Injuries
There are four main types of electrical injuries:
• Direct:
Electrocution or death due to electrical shock
Electrical shock
Burns
• Indirect - Falls
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Electrical Shock
Received when current passes
through the body
Severity of the shock depends on:
1. Path
2. Amount of current
3. Length of time
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LOW VOLTAGE DOES NOT
MEAN LOW HAZARD
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Effects of Electric Current on the
Human Body
• 1 mA (milliamp) Barely perceptible
• 16 mA Max “let go” current
• 20 mA Paralysis of respiratory muscles
• 100 mA Ventricular fibrillation
• 2 Amps Cardiac standstill and internal organ damage
• 15/20 Amps Fuse/breaker opens circuit
* mA = milliampere = 1/1,000 of an ampere
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Dangers of Electrical Shock
Currents more than 75 mA
can cause a rapid,
ineffective heartbeat --
death will occur in a few
minutes unless a
defibrillator is used
Defibrillator in use
75 mA is not much current – a small power drill uses 30 times
as much
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Ground-Fault Circuit Interrupter
• This device protects you from
dangerous shock
• The GFCI detects a difference in
current between the positive and
neutral wires
(This could happen when electrical
equipment is not working correctly,
causing current “leakage” – known as
a ground fault.)
• If a ground fault is detected, the GFCI
can shut off electricity flow in as little
as 1/40 of a second, protecting you
from a dangerous shock
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Burns
• Most common shock-related
injury
• Typically occurs on hands
• Very serious injury that
needs immediate attention
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Falls
• Electric shock can also
cause indirect injuries
• Workers in elevated
locations who experience a
shock may fall, resulting in
serious injury or death
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Electrical Hazards and How to
Control Them
Why?
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Electrical accidents are caused
by a combination of three factors:
1. Unsafe equipment and/or
installation,
2. Workplaces made unsafe by
the environment, and
3. Unsafe work practices
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Grounding
Grounding creates a lowresistance path from a tool
to the earth to disperse
unwanted current.
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Tools -Preventing Electrical Hazards
• Inspect tools before use
• Use the right tool
correctly
• Use double insulated
tools
• Others?
Double Insulated marking
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Exposed Electrical Parts
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Control – Isolate Electrical Parts
• Use guards or barriers
• Replace covers
What about 50 volts or more?
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Control – Close Openings
• Junction boxes, pull
boxes and fittings must
have approved covers
• Unused openings in
cabinets, boxes and
fittings must be closed
(no missing knockouts)
Photo shows violations
of these two requirements
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Overhead Power Lines
Equipment that can
contact power lines?
What is the minimum
distance?
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Cords & Wires
Cords can be damaged by:
Aging
Door or window edges
Staples or fastenings
Activity in the area
Remove cords by pulling on the plugs, not the cords
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Clues that Electrical Hazards Exist
• Tripped circuit breakers or
blown fuses
• Warm tools, wires, cords,
connections, or junction
boxes
• GFCI that shuts off a circuit
• Worn or frayed insulation
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Safety-Related Work Practices
Avoid Wet
Conditions!
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No Bare Ground on Temp Circuits
Romex
No Ground
No
Strain Relief
Temp Cord
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GFCI Needed
Exposed Elec. Conductor
Splices
1910.303(c)
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No Ground
1910.304(f)(4)
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You Find the Standard
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1910.305(g)(2)(iii)
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Flex Cords Protected From Damage
1910.305(a)(2)(iii)(g)
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Too Many Conductors
Per Conduit
1910.305(b)(2)
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Improper Use of Junction Box
1910.305(g)(1)
Flex Cord Protection
1910.305(a)(2)(iii)(G)
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Flex Cords-Continuous
Length
1910.305(g)(2)(ii)
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Exposed Elec. Conductor
1910.303(g)(2)(i)
Strain Relief
1910.305(g)(2)(iii)
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50v or more shall be guarded
1910.303(g)(2)(i)
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Equip. Free From Recognized Hazards
1910.303(b)(1)
Metal Shavings
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Machine Guarding???
Exposed Elec. Parts
1910.303(g)(2)(i)
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(g)(2)(No Strain Relief
1910.305(g)(2)(iii)
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Exposed Thermostat
1910.303(g)(2)(i)
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Summary
Electrical equipment must be:
 Listed and labeled
 Free from hazards
 Used in the proper manner
If you use electrical tools you must be:
 Protected from electrical shock
 Provided necessary safety
equipment
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The movement of electricity
measured in amps is called
A.Voltage
B.Current
C.Resistance
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A conductive connection to the
earth which acts as a protective
measure is called.
A. Resistance
B. Current
C.Grounding
D.Insulator’’
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The most common electrical
related injury is
A. Falls
B. Electrical burns
C. Electrocution
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How many amps can cause
your heart to go into
ventricular fibrillation.
A. 75 mA
B. 15 Amps
C. 20 Amps
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At what voltage is an
electrical conductor
required to be protected
against contact?
A. 50 volts
B. 120 volts
C. 30 volts
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Credits
• Some photos from safteng.net used with permission.
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presentation are from numerous sources, most of
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