ELECTRICAL SAFETY
INTRODUCTION
Equipment such as centrifuges, refrigerators, freezers, hot plates, stirrers, vacuum pumps,
mixers and blenders, electrophoresis apparatus, water baths, sonicators, power supplies,
microwave ovens, etc are essential electrical devices found in the laboratories. These
devices can pose a major hazard to laboratory workers, particularly when mishandled or not
properly maintained. They may carry even more risks if they have high voltage or high
power requirements. It is therefore very important that all work activities are conducted with
electrical safety in mind, and that equipment adheres to electrical safety codes. Laboratory
workers should be adequately trained in the safe and proper use of laboratory equipment
before they are allowed to operate them.
OBJECTIVE
The objective of this guide is to provide laboratory personnel with the necessary information
to enable them to work with laboratory electrical equipment safely.
SCOPE
This document is applicable to all staff and students working in the laboratories of the
Department of Medicine.
ELECTRICAL HAZARDS
(a) Shock
Electrical shock happens when the body becomes part of the electric circuit. When
this occurs, the individual either comes in contact with both wires of an electrical
circuit, one wire of an energized circuit and the ground, or a metallic part that has
become energized by contact with an electrical conductor. The factors that
determine the effects and severity of an electrical shock are the pathway through
the body, the amount of current, the length of time of the exposure, and whether the
skin is wet or dry (water is a great conductor of electricity). An electric shock can
disrupt normal functioning of muscles, most significantly the heart. It may cause the
heart to lose its coordination or rhythm.
(b) Electrical Burn
If a strong electrical current passes through the body, internal damage such as
cardiac arrest can occur. An electrical burn may appear insignificant or not show on
the skin at all, but the damage can extend deep into the tissues under the skin.
Sometimes an electrical burn can cause the individual to be thrown off by a jolt or to
fall, resulting in fractures or other associated injuries.
(c) Arc Flash
The majority of people admitted to hospitals due to electrical accidents are from arc
flash burns and not from shock. Arc flash burns are caused when an electric current
passes through air between ungrounded conductors and grounded conductors.
There may be 1 to 2 explosions within milliseconds, which can generate
temperatures between 5,000 and 35,000oF. The pressure wave from an arc blast
can be very similar to an explosion from a hand grenade
(d) Electrical Explosion
Explosions occur when electricity ignites an explosive mixture in the atmosphere.
Explosive atmospheres result from the accumulation of flammable vapors or gases
from nearby sources and processes. Ignition sources can be overheated conductors
or equipment, or normal arcing (sparking) at switch contacts.
(e) Electrical Fire
Electrical fires can claim lives and injure people. While some electrical fires are
caused by electrical system failures and equipment defects, many more are caused
by the misuse and poor maintenance of electrical equipment, incorrectly installed
wiring, and overloaded circuits and extension cords.
POWER FAILURE
Power failure or outage can create hazardous situations. For example, fume hoods
may stop operating, allowing vapors to be released into the laboratory. When a
freezer or refrigerator fails, chemicals may warm and release flammable or toxic
vapors. If magnetic or mechanical stirrers fail to function, safe mixing of reagents
may be compromised.
PRACTICES AND PROCEDURES
1. PREVENTING ELECTRICAL HAZARDS
Laboratory workers can significantly reduce electrical hazards by following the basic
precautions below:
(a) Insulation
It is particularly important to examine electrical equipment cords in the
laboratory before each use, since corrosive chemicals or solvents may erode
the insulation. Damaged cords should be replaced, especially in wet
environments such as cold rooms and near water baths.
(b) Guarding
Live parts of electric equipment operating at 50 volts or more must be
guarded against accidental contact. Plexiglas shields may be used to protect
against exposed live parts, especially in electrophoresis devices.
(c) Grounding
Use only equipment with three-prong plugs in the laboratory. The third prong
provides grounding for internal electrical short circuits, and thus protects the
user from a potential electrical shock.
(d) Electrical protective devices
Circuit protection devices such as ground-fault circuit interrupters, circuit
breakers and fuses are 3 well-known electrical protective devices which are
designed to automatically limit or shut off the flow of electricity in the event of
an overload or short circuit or ground-fault in the wiring system. Fuses and
circuit breakers provide overload protection which is very useful for
equipment (e.g. vacuum pumps, stirrers, drying ovens, etc) that is left on for
extended periods of time. They prevent over-heating of wires and
components that might otherwise create fire hazards by disconnecting the
circuit when it becomes overloaded.
(e) Motors
Where volatile flammable materials are used in the laboratory, motor-driven
electrical equipment such as blenders, stirrers, hotplates, etc should be
equipped with non-sparking induction motors or air motors. These motors
must conform to explosion resistance requirements. Unless flammable
vapors are adequately controlled, equipment with sparking induction motors
should not be used. Although some newer equipment has spark-free
induction motors, the on-off switches and speed controls may produce a
spark when they are adjusted because they have exposed contacts. One
way to solve this is to remove any switches located on the device and insert
a switch on the cord near the plug end.
2. ELECTRICAL COMPONENTS
(a) Plug
•
Use only plugs that has been approved by the Safety Authority
•
When inserting into a socket, make sure that the plug is fully
inserted.
•
Plugs should never get wet
•
Look out for hot plugs, fuses that blow frequently, scorch marks
on plugs - these are signs of loose wiring or other problems that
should be fixed. Call the electrician.
•
All broken or damaged plugs are to be replaced immediately.
•
Always switch off the electrical supply before taking out the plug
from the socket.
•
Make sure the wires are held firmly in place inside the plug
(b) Socket
•
All sockets should be firmly mounted onto the wall or mounting
location.
•
Broken sockets should be replaced immediately.
•
Sockets should never get wet
•
Look out for hot sockets, scorch marks on sockets - these are
signs of loose wiring or other problems that should be fixed. Call
the electrician.
•
An overloaded socket when too many electrical appliances are
plugged into it can lead to overheating and fire
(c) Electrical cords
•
If cords are hidden under pieces of rags, cloth or combustible
materials they can overheat and can cause a fire.
•
Electrical cords should be in good condition. Fires also start when
old, frayed or otherwise-damaged cords are used. They pose an
electrocution hazard to personnel too. Replace them.
•
Electrical should not be anywhere that they could be tripped over,
or near water, or any sources of heat
•
Secure all electrical cords to prevent falls/trips accidents. Cords
can be damaged by traffic too.
•
Although extension cords are a useful temporary tool, they can
be dangerous if safety precautions are not followed. Overloaded
extension cords can overheat and start a fire. Install sufficient
electrical outlets to support the many electrical equipment used in
the laboratory.
•
When not using electrical equipment, switch it off, unplug it and
store the electrical cord carefully to avoid damage.
(d) Fuses
When fitting or replacing a fuse, it is important to use the right fuse for
the appliance to make sure the fuse does not overheat. Check the
equipment manual or look on the equipment to find out its wattage and
then use the correct fuse:
•
for appliances up to 700 watts, use a 3 amp fuse
•
for appliances between 700 and 1,000 watts, use a 5 amp
fuse
•
for appliances more than 1,000 watts, use a 13 amp fuse
(e) Electrical Wiring
Electrical wiring is a job for a person with experience. An electrical fire
can start easily if the wiring installed is not done to minimum electric
code standards. Get a qualified electrician to do the job. Remember,
wrong wiring can cause fires and kill people

The color codes for electrical wiring are:
Live wire - brown
Neutral - blue
Earth - green / yellow
3. SAFE PRACTICES
To reduce risk of injury or fire when working with electrical equipment,
observe the following:
a) All electrical equipment must meet local safety standards and
requirements
b) Consider electrical loading of equipment prior to purchase and
installation
c) Follow manufacturer’s operating and maintenance instructions
d) Never handle electrical equipment with wet hands
e) Do not touch energized electrical circuits.
f) Disconnect equipment before servicing or repair
g) Minimize the use of electrical equipment in cold rooms or areas
where there is condensation
h) If water or chemical is spilled onto equipment, shut off power at the
main switch and unplug the equipment before dealing with the spill
i)
Do not place electrical equipment near flammable / combustible
materials
j) If an individual comes in contact with a live electrical conductor, do
not touch the equipment, person or cord – if possible, turn off the
source of electricity immediately or remove the source away from the
injured person using a non-conducting object such as wood, plastic
or cardboard, etc
k) Use guarding around exposed circuits and sources of live electricity
(e.g. electrophoresis device)
l) Electrical equipment should be regularly checked for signs of wear
and tear and properly maintained.
4. HIGH VOLTAGE OR CURRENT / INSTALLATION AND REPAIR OF EQUIPMENT
Repairs of high voltage or high current equipment should be performed only
by trained electricians.
No one in the laboratory is allowed to carry out any electrical installation and
maintenance where there is a possibility of getting into contact with live
wiring or terminal.
Faulty electrical equipment should be reported to the person in-charge of the
laboratory and Safety Committee Chairman immediately. Place a sign
“DANGER – DO NOT USE” on the equipment and make arrangements for
repair by the service engineer.
5. EMERGENCY AND FIRST AID
See Safety Manual (Emergency Preparedness and Emergency
Procedures) for more information.
(a) Electrical Fire
If there is an electrical fire, pull the plug out, or switch off the power at the
fuse box - if it is safe to do so. Sometimes this can stop the fire immediately.
Never use water on an electrical fire, and don't take any risks with personal
safety – get out and stay out and call Fire – SCDF (995), NUS Campus
Security (68741616) or NUH Security (67725558).
(b) Electrical burn:
Call 995 (SCDF Ambulance), 67725222 (NUH Emergency Service)
immediately. While waiting for medical assistance, follow these procedures:
i.
Look first but don't touch. If the person is still in contact with the
electrical source, touching may pass the current through to you.
ii.
If possible, turn off the source of electricity. Otherwise, move the
source away from both the injured person and you using a dry nonconducting object made of cardboard, plastic or wood.
iii.
Check for signs of circulation (e.g. breathing, coughing or
movement). If absent, commence cardiopulmonary resuscitation
(CPR) immediately.
iv.
Prevent shock. Lay the person down with the head slightly lower
than the chest and the legs raised up.
v.
Cover the affected areas. If the person is breathing, cover any
burned areas with a sterile gauze bandage, if available, or a clean
cloth. Do not use a blanket or towel as loose fibers may stick to the
burnt areas.
(c) Electrical shock:
Call NUH Emergency (Tel: 67725222) or NUS Campus Security (68741616)
immediately if any of these signs and symptoms occur:
•
Respiratory failure
•
Cardiac arrest / heart rhythm problems
•
Muscle pain and contractions
•
Seizures
•
Numbness and tingling
•
Unconsciousness
While waiting for medical assistance, follow the following steps:
i.
Look first but don't touch. If the person is still in contact with the
electrical source, touching may pass the current through to you.
ii.
If possible, turn off the source of electricity. Otherwise, move the
source away from both the injured person and you using a dry nonconducting object made of cardboard, plastic or wood.
iii.
Check for signs of circulation (e.g. breathing, coughing or
movement). If absent, commence cardiopulmonary resuscitation
(CPR) immediately.
iv.
Prevent shock. Lay the person down with the head slightly lower
than the chest and the legs raised up.
Exercise the following caution:
•
Do not go near high-voltage wires until the power is switched off.
Stay at least 20 feet away and farther if wires are jumping and
sparking.
•
Do not touch the person with bare hands if the person is still in
contact with the electrical current.
•
Do not move the person unless the person is in immediate danger.
6. INCIDENT AND ACCIDENT REPORTING
All incidents or accidents and injuries are to be reported by the department
Safety Committee Chairman to OSHE within 24 hours via online reporting,
termed as “Accident/Incident Reporting System” (AIRS) using the following link:
https://staffweb.nus.edu.sg/oshe/submit_airs.htm. A full list of accident / incident
contact numbers is available in the Safety Manual (Emergency Preparedness
and Emergency Procedures).
Revised by Safety Website Team
Revised on 16 July 2012
Endorsed by Professor Ho Khek Yu
Head
Department of Medicine