Electrician Environmental Safety
Here is a great summary of environmental considerations from Cornell
Occupational electrocutions continue to be a serious problem throughout
the United States. Data obtained from the Bureau of Labor Statistics' Annual
Survey indicate that approximately 10% of all occupational fatalities are due
you are not a qualified electrician you should not be servicing any electrical
equipment. If you are a qualified individual, always be aware of your work
environment and exercise safe working procedures.
Electrical Safety Guidelines
work area clean and orderly. This reduces the chance of accidents and prevents
the accumulation of combustibles as well as flammable materials in the
work around a source of electricity when you, your surroundings, your
clothing, or your tools are wet.
all metal jewelry, rings, and watches before working on electrical equipment.
all tools before use for damaged housing and frayed or damaged power cords.
insulated hand tools and double insulated power tools.
remove the 3rd grounding prong from an electrical cord.
remove frayed or defective extension cords from the workplace.
Ground Fault Interrupters (GFI’s) when working outside, near wet areas or
when using extension cords. GFI’s help to protect you from serious
electrical shocks and burns by sensing the amount of current going into the
piece of equipment and the amount of current going out. If this current
differs by as much as 5 milliamps the GFCI will trip within 1/40 of a second.
To learn more about GFI’s click on "When
to use GFI’s and how they work".
at least 10 feet clearance while working near overhead power lines.
emergency medical care can be lifesaving for workers who have
contacted either low voltage or high voltage electric energy.
Immediate cardiopulmonary resuscitation (CPR) followed by advanced
cardiac life support (ACLS) has been shown to save lives.
Whenever you must work on electrically powered equipment at CHESS, you
must the follow appropriate CHESS LNS Lockout/Tag-out procedures outlined
below. If you
have not been trained in CHESS-specific Lockout/Tag-out procedures,
contact the CHESS Operator or Dave Jones to receive training before you
attempt to use Lockout/Tag-out tags or work on any electrically powered
equipment or device.
If you see a piece of equipment with a red lockout/tag-out tag attached,
you may not attempt to start, use, or energize that piece of equipment.
Equipment-specific procedures for CHESS equipment are kept in the
procedures notebook (also available from Steve Grayat LNS) on the Operator
Desk, along with Lockout tags and locks. You must sign out tags and locks in
the log book provided.
Procedures that effect the control of hazardous energy require:
shutting off the equipment or machine;
locating the energy isolating devices and isolating the equipment or
machinery from them;
locking or tagging out the energy isolating devices;
reducing or eliminating stored residual energy;
verifying the effectiveness of the energy isolation.
Click here for Cornell EH&S Self-Inspection Checklist for appropriate Lockout/Tagout
Dangers and Injuries Associated with Electricity
There are several ways in which personal injury may be caused:
1. Personal Injury
Electric shock is the effect produced on the body, particularly its
nervous system, by electric current passing through it, and its effect depends
on current strength (which in turn depends on voltage) the path the current
takes through the body, the surface resistance of the skin and several other
A voltage as low as 15V can produce discernible shock effects and 70V has
been known to cause death. Generally speaking however, fatalities occur from
this cause at the normal domestic and industrial voltage of 240V A.C. and from
currents of 25-30 milliamps.
The consequences of electric accidents are first of all related to the
type of electric risk to which a person is exposed. In second place, to the
physical characteristics of the person involved, and, finally, to the context
of the installations and the environment, which can escalate from a simple
scare by contractions caused by a brief touch, up to loss of life.
RESULTS OF PHYSICAL CONTACT WITH CURRENT/VOLTAGE
k (60 Hz)
Less than 1.0 mA
From 6.0 to 8.0 mA
From 8.0 to 25 mA
From 25 to 50 mA
From 50 to 100 mA
More than 100 mA
Loss of control, asphyxia
Shock, cardiac arrest
Consequences of Low-Voltage Contacts
Contrary to their name, low voltages in normal service are very risky due
to their intensive use in all daily activities, which increases the
probability of accidents.
The most dangerous Direct Contacts, are those which occur under
humid conditions, followed by dry contacts. In both cases, a prolonged contact
of more than 3 seconds causes, first of all, ventricular fibrillation and then
death by asphyxia and/or cardiac arrest. The blood and lymph liquids and
muscular water continue boiling and vaporizing until carbonization occurs.
The insertion of a resistance, in the case of Indirect Contacts,
usually permits an instinctive evasive reaction by the person involved,
causing only sharp contractions and distensions of the striated muscles,
giving the impression of having been strongly "thrown", which could
cause another type of accident due to the fall.
of Medium and High Voltage Discharges
Despite the gradients that originate the discharge process, Medium and
High Voltages in normal service are statistically a lower risk probability
because they are not massively used and involves crossing safety or security
barriers. Nevertheless, their consequences, although not always lethal, can be
disastrous for the victim.
In discharges from an energized conductor, the electric power
arc that is formed has a current equivalent to that of a short Grounding-Phase
circuit, but it closes at the end of its action time, which permits speedy
In discharges from a charged but out-of-service conductor, the
electric arc involves transmission of a large amount of electric power in a
brief instant, with a current that diminishes drastically and tends to remain
at low intensity. Rescue must be carried out very carefully.
of Voltages due to a Major Grounding Fault
Accidents by potentials due to the dispersion of soil grounding faults,
both in substations and in electric line structures, have a low case history
and low probability of occurrence, both due to adequate designs of grounding
systems and because they are sometimes distant from the pedestrian traffic in
such installations, which are also surrounded by clearance or easement areas.
However, accidents by poor control of these potentials are usually lethal due
to shock or cardiac arrest for the people and any large animals involved.
Touch Voltages are the ones that cause the larger voltage gradients
inside substation yards or at the foot of electric line structures or
Passing Voltages inside substations originate lower voltage gradients.
However, these can be higher in the periphery of the same and of electric
line structures and supports.
The most common cause of death from shock is suffocation and it is highly
desirable that persons dealing with electricity should be trained in
resuscitation, with practice in both artificial respiration and in cardiac
Minor shocks may not in themselves be serious, but can lead to serious
consequences, for example, the muscle contraction which they cause may lead to
falls from working platforms or ladders.
These are caused by the passage of heavy current through the body or by
direct contact with an electrically heated surface. They may also be caused by
the intense heat generated by arcing from a short-circuit. All cases of burns
require immediate medical attention.
Where flammable gases or vapours are present, special care is necessary in
the design and selection of electrical equipment. In such areas, all equipment
should be fully flameproof.
In some cases it is simpler and more economic to isolate the electrical
equipment from the flammable vapours - for example with refrigerators used to
store flammable solvents the thermostat should be mounted external to the
cabinet so that any sparking which occurs is harmless. DO NOT STORE
SOLVENTS IN NON-SPARK PROOF REFRIGERATORS OR FREEZERS.
Fires may be caused by any of the following:
A spark arises from a sudden discharge through the air between two
conductors, or from one conductor to earth. The current produced is usually
small, so that serious fires are unlikely unless explosive gases or vapours
are present, or highly flammable material is in contact with the conductor.
(b) Short Circuits
A short circuit is formed when the current finds a path from the outward
conductor wire to the return wire other than through the equipment to which it
is connected. The current flow may be large because of the low resistance of
the leads, and arcing often occurs at the contact between the conductors.
Insulation may, therefore, be burned and set fire to adjacent flammable
(c) Overloading and Old Wiring
Wiring must not be overloaded, otherwise it will overheat and the
insulation will be damaged. This can lead to a short circuit at some point in
the length of the conductor, or more likely at connection points.
The insulation of wiring which has been in use for a number of years tends
to become brittle, and where alterations or additions are required, the
installed cable must always be checked by a competent electrician, and
replaced completely if there are indications of failure of the insulation.
3. Safety Measures
Cables must be of sufficient size to carry the current which can flow
through them in both normal and abnormal conditions and must be adequately
insulated for reasons of safety and of preventing mechanical damage. Those
cables which provide the basic services within a building are normally housed
in conduit or troughs: particular care is required where apparatus is wired up
from socket outlets, and where no such permanent protection is feasible. Such
cable must be sufficiently robust to withstand the wear and tear of laboratory
use, and fully waterproof where water supplies may be available within the
vicinity of the apparatus. Protection against insulation failure must be
provided by either fuse or circuit breaker.
This device will open a circuit when a predetermined excess of current
flows. It may be the rewirable type, or alternatively, may incorporate a wire
embedded in insulating powder within a cartridge case. The cartridge fuse is
generally more satisfactory.
This is a form of switch which opens automatically if the circuit it
controls is overloaded: it may operate on either a thermal or magnetic
principle. It is essential to select the correct rating of fuse or circuit
breaker for any particular current.
The external metal casing of electrical apparatus, cables and conduit must
be earthed as a legal requirement. The reasons for this are:-
(i) to prevent the casing rising to a dangerous voltage if some fault
arises, for example, a short-circuit between conductors and casing;
(ii) to conduct any current away by a safe path;
(iii) to ensure that a faulty circuit is automatically disconnected from
the supply by drawing sufficient current to blow the fuse or operate the
New equipment should always be checked to ensure that it is properly
earthed before putting it into use.
The circulation space in laboratories and workshops must be kept clear to
prevent hazards from tripping.
(e) Small Equipment and Tools
Electrical equipment and tools in laboratories and workshops should be
regarded as being in normal industrial use, and every precaution for safe
handling must be taken. This category would include:
Lamps and measuring instruments
Electrical machines to provide mechanical loads or drives
Power tools and soldering irons to work on apparatus
In all instances the connection of these items of equipment to the mains
must be correctly made by a competent person.
If you are connecting a plug, make sure the wires are connected to the
Remove only the required amount of insulation so that no bare conductors
are exposed when the connections are made, and remove any "whiskers"
which may be present.
In general, permanent apparatus having an incidental use in experimental
and research work should be:
i) Fully insulated, with switches and terminals enclosed and protected.
ii) Correctly fused, so that the maximum current required can be supplied
by any fault is limited to the minimum possible.
iii) Correctly connected to the supply, the line being fused and switched
with the earth pin connected. The switch must be inserted into the line or
iv) Inspected and tested at regular intervals of about a year for earth
continuity and general condition.
v) Provided with isolating switches, fuses or plugs, so that they may be
removed before the equipment is dismantled.
iv) Not overloaded, a proper consideration of the load magnitude should be
made before the apparatus is connected to the supply.
Do not take chances, if in doubt seek assistance and advice.
Case Studies 1:
1. A worker was changing the bulb in a light fixture that had been
incorrectly wired (polarity was reversed). He inadvertently touched the
metal base of the bulb while it was in contact with the socket. He received
a severe shock and later died in hospital.
2. On July 29, 1985, a
29-year-old welder was electrocuted when he inserted the "male" end
of an electrical plug on a portable arc welder into a broken
"female" connector of an extension cord. As in the previous case,
the victim inserted the ground prong of the welder cord 90 degrees clockwise
away from the appropriate ground terminal of the extension cord, and the metal
casing of the welder connector became energized. It appeared that the
connector on the extension cord had been damaged by everyday use or abuse
(being thrown down on and dragged across concrete floors, being run over by
industrial equipment, etc.)2
Caution should be used around ALL electrical circuits and
equipment. The potential for electric shock should never be underestimated.
Employers and other groups should regularly emphasize the safe use of
electricity in the workplace. Continuous efforts must be made to prevent
electrical injuries and deaths due to damaged receptacles and connectors.
Case Studies 2:
Case #1--SUCCESSFUL RESUSCITATION
A 30-year-old construction worker was working on a fire escape in a
building being renovated. Another worker handed the victim a metal pipe, and
he was holding it with both hands when it contacted a nearby high voltage
line, completing a path-to-ground. The worker instantly collapsed from this
contact with electrical energy. Approximately 4 minutes after he collapsed,
the fire department rescue squad arrived and began CPR. Within 6 minutes, a
paramedic unit was on the scene providing defibrillation and other ACLS
measures. They were able to establish a heartbeat and pulse, but the
individual continued to require respiratory support during transport to the
hospital. He regained consciousness and was discharged within two weeks. He
did have to return for further medical care for burns he received on his hands
(current entrance) and buttocks (current exit) .
Case #2--UNSUCCESSFUL RESUSCITATION
An 18-year-old male restaurant worker contacted electrical energy when he
kneeled to plug a portable electric toaster into a 100-120 V/20 amp floor
outlet. After a scream was heard, the victim was found convulsing on the damp
floor, with one hand on the plug and the other on the receptacle box. The
assistant manager went to the electrical panel, but was unable to locate the
appropriate circuit breaker. A coworker attempting to take the victim's pulse
received an electrical shock, but was not injured. After telephoning the
emergency medical service, the assistant manager returned to the panel and
de-energized all of the circuits (3 to 8 minutes after the worker contacted
electrical energy). The injured worker was covered with a coat to "keep
him warm." After about 5 minutes, another call was placed to the
emergency squad, and the assistant manager "yelled" for an off-duty
employee who lived in an apartment across the lot, who came and began CPR. The
emergency service was on the scene 10 minutes after receiving the first call.
ACLS measures were available but the resuscitation was unsuccessful and the
worker was pronounced "dead on arrival" at the local hospital. The
exact time span between the worker contacting electrical energy and the
beginning of CPR is unknown, but it is reasonable to assume that it was longer
than 4 to 6 minutes. Paramedics with ACLS capability arrived 10 minutes after
receiving the call, but more than 10 minutes after the accident occurred .
In Case #1, basic life support was begun within 4 minutes by the fire
department rescue squad who happened to be stationed nearby. They were
experienced and had up-to-date knowledge in CPR techniques. In this case, CPR
was begun within the 4-minute recommendation. An ambulance, equipped and
staffed to provide ACLS, arrived within 6 minutes. The standards and
guidelines  for CPR within 4 minutes, and ACLS within 8 minutes, were met
and the worker did survive.
In Case #2, the worker's contact with electrical energy was prolonged and
a coworker who aided him received an electrical shock, because coworkers did
not know how to de-energize the circuit. The optimal times for CPR and ACLS
were exceeded, and the resuscitation was unsuccessful. Providing appropriate
medical care after an electrical energy incident will not guarantee success.
However, it has been reported elsewhere  and supported in the NIOSH case
reports, the chance for successful resuscitation after cardiopulmonary arrest
is best when the criteria for providing emergency medical care are met.
Recommendations for Electrical Safety in the Workplace
NIOSH makes the following recommendations in these areas:
1. PROPER UTILIZATION OF ELECTRICAL SYSTEMS
All receptacles and
connectors should be used only in accordance with the manufacturers'
specifications, and the specific listing for the item as set forth by
nationally recognized testing laboratories. Users should be advised of the
importance of using receptacles and connectors only for applications for which
they have been designed. When a component is selected for use, it should be
evaluated to determine if it can tolerate the environment to which it will be
exposed. Physical abuse and stress on these components should be minimized by
the selection of a safe location and by the use of stress/strain relief
2. AWARENESS AND RECOGNITION OF HAZARDS
Policies that address the
proper use of receptacles and connectors should be developed and implemented
by qualified safety personnel. Safety training should emphasize awareness and
recognition of electrical hazards associated with receptacles and connectors
(i.e., broken receptacles and connectors, improper electrical connections,
damaged cords, the importance of grounding, etc.). Immediate corrective action
should be taken when damaged components or safety hazards are encountered.
When safety policies and procedures are developed, they should be enforced.
3. PERIODIC INSPECTION AND MAINTENANCE OF ELECTRICAL SYSTEMS
should be conducted for all electrical system equipment and components in
order to identify all electrical hazards present. Records should be kept of
any electrical hazards identified, and appropriate corrective action should be
taken immediately. These periodic inspections should be supplemented with
daily inspections by the personnel using this equipment.
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