Electrical Hazards

On Oct 22, 2012

Persons responsible for the general maintenance and upkeep of electrical installation should be trained for the job for which they are specifically appointed and authorised. They should be conversant with the procedures to be adopted while working on the installations, safety precautions to be taken while working, first aid to be given to persons suffering from electric shock, use of fire-fighting equipment, etc.

1. Introduction

Electricity is essential to modern life, both at home and on the job. It has become such a familiar part of our daily life. However, we tend to overlook the hazards electricity poses and fail to treat it with the respect it deserves. Electricity is often referred to as a “silent killer”, because it cannot be tasted, seen, heard, or smelled. It is essentially invisible. According to the National Crime Records Bureau of India, death due to electrocution averages around 25.06 deaths per day (9149 in 2010).

The hazards associated with the use of electricity can affect any one. Many electrical devices, such as hot plates, stirrers, vacuum pumps, lasers, microwave ovens, water heaters, etc., can pose a significant hazard particularly when mishandled or not maintained. Electricity has long been recognized as a serious workplace hazard, exposing employees to electric shock, electrocution burns, fires and explosions. Sparks from electrical equipment can serve as an ignition source for flammable or explosive vapours. Even loss of electrical power can result in extremely hazardous situation, For example, flammable or toxic vapours may be released as a chemical warms when a refrigerator or freezer fails.

The major hazards of electricity are electric shock, electrical arc – flash, electrical arc – blast. This article will highlight various hazards of electricity and how to prevent them.

2. What is electricity?

Electricity is a form of energy, which cannot be destroyed. It is weightless and behaves like an imaginary fluid, which can move freely through some substances called conductors. In electricity the source is the power generating station. Current travels through electrical conductors in the form of wires; and pressure, measured in volts, is provided by a generator. Resistance to the flow of electricity is measured in ohms and varies widely. It is determined by three factors, viz.

the nature of the substance itself
the length and the cross – sectional area (size) of the substance
the temperature of the substance.

Electricity flows more easily through some materials than others. Some substances such as metals generally offer very little resistance to the flow of electric current and are called “conductors”. A common conductor is the surface of the earth. Glass, plastic, porcelain, clay, pottery, dry wood, and similar substances generally slow or stop the flow of electricity and they are called “insulators”. Even air, normally an insulator, can become a conductor, as occurs during and arc or lightning strike. Water is a great conductor of electricity, allowing current to flow more easily in wet conditions. Pure water is a poor conductor. But small amount of impurities in water like salt, acid, solvents, or other materials, can turn water itself and the substances that generally act as insulators into conductors or better conductors.

For example, dry wood, generally slows or stops the flow of electricity. But when saturated with water, wood turns into a conductor. The same is true of human skin. Dry skin has a fairly high resistance to electric current. But when skin is moist or wet, it acts as a conductor. This means that anyone working with electricity in a damp or wet environment needs to exercise extra caution to prevent electrical hazards.

3. Dangers from electricity

The dangers associated with the use of electricity may be classified as:

Injury from direct contact:
– Injury by shock.
– Injury from internal burns.
Injury without current flow through body:
– Direct burns from electric arcs, spattered molten metal, etc.
– Radiation burns from very heavy arcs.
– Physical injury from false starting of machine, failure of crane controls, explosion of switchgear, etc.
– Injury from fire and explosion from electric ignition of flammable vapours, gases, liquids and solids.
– Eye injury from electric arcs,
Eye injury from current flow induced in or near the human body by intense electric magnetic fields:
– Injury from elevation of whole body temperature.
– Local injury such as cataract formation in the eye.
– Burns due to metallic objects such as rings, dental metal in close contact with local part of body.

4. How shock occurs?

Everyone has received minor electric shocks sometime or the other, which are no cause for concern. But once in a while, a loose wire or a faulty household appliance can shock the life out of you. Electricity travels in closed circuits, normally through a conductor. But sometimes a person’s body- an efficient conductor of electricity – mistakenly becomes part of the electric circuit. This can cause an electrical shock. When you receive a shock, electricity flows between parts of your body or through your body to a ground or the earth. In short, when your body becomes a part of the electric circuit, shock occurs. Electricity can travel only in a closed or looped circuit. Normally, the travel is through the conductor. The shock occurs, when the current enter your body at one point and leave at another. Electrical shock occurs either when an individual comes in contact with:

both wires of an electric circuit,
one wire of an energized circuit and the ground,
a metallic part that accidentally becomes energized by contact with an electrical conductor

Remember, you don’t have to touch a power line to be electrocuted. If you come within three meters of a power line, the energy can arc towards you and take a path to the ground. Never prune trees that grow next to power lines because electricity can move through the tree or jump towards you, if you are within three meters. Not all overhead wires entering houses and buildings are insulated and therefore cannot protect you from an electric shock. Though there is weather proofing material around them, they can become brittle and crack. Also be aware of overhead power lines when moving ladders around your house.

5. Severity of the shock

The severity and effects of an electrical shock depends on a numbers of factors, such as;

The path of the current through the body
The amount of current flowing through the body
The length of the time of the exposure and
Whether the skin is wet or dry.

5.1 Effects of current on human body

The effects of current on human body vary from person to person, which mainly depend upon the quantity of current, pathway through the body, duration of exposure, and type of current. The Table 1. Show the effect of current on human body. The Table demonstrates a general relationship for a 60 cycle, hand–to–foot shock of one second’s duration. It may be noted from Table 1 that a difference of less than 100 milliamperes exits between a current that is barely perceptible and one that can kill. It may also be noted that most electrical circuits can provide, under normal conditions, up to 20,000 milli-amperes of current flow.

5.2. AC and DC Shock Comparison

The minimum current a human can feel depends on the current type i. e. AC. or DC. and frequency. A person can feel at least 1 mA of AC at 60 Hz, while at least 5 mA for DC. The Table 2 illustrates comparisons between AC and DC shock.

6. Burn and other injuries

The most common shock related to injury is burn. Burns suffered in electrical accidents may be of three types, viz.

Electrical burns,
Are burns or Flash burns
Thermal contact burns.

**Table 1. – Effects of Current on Human Bod**
urrent Level mA ( In milliamperes)	Symptoms
1 mA	Perception level. Slight tingling sensation. Still dangerous under certain conditions (water / wet conditions)
5 mA	Slight shock felt; not painful but disturbing. Average person can let go. However, strong involuntary reactions to shocks in this ranges may lead to injuries (Muscular contraction can prevent the victim from getting free)
6 – 30 mA	Painful shock, muscular control is lost. This is called the freezing current or “let – go” range
50 – 150 mA	Extreme pain, respiratory arrest, Severe muscular contractions.* Individual cannot let – go. Death is possible
100 mA – 3 Seconds	Ventricular fibrillation (the rhythmic pumping action of the heart ceases )
200 mA – 1 Second	Ventricular fibrillation
1000 mA – 4300 mA	Ventricular fibrillation. Muscular contraction and nerve damage occur, Death is most likely
10,000 mA	Cardiac arrest. Severe burns and probable death

* If the extensor muscles are excited by the shock, the person may be thrown away from the circuit.

**Table 2. – AC and DC Shock Comparison**
AC (60 Hz )(mA)	DC (mA)	Effects
0.5 – 1.5	0 – 4	Perception
1 – 3	4 – 15	Surprise (Reaction)
3 – 22	15 – 88	Reflex Action (let–go)
21 – 40	80 – 160	Muscular Inhibition
40 – 100	160 – 300	Respiratory Block
>100	>300	Usually Fatal

6.1. Electrical burns:

Electrical burns are the result of the electrical current flowing through tissues or bone, generating heat that causes tissue damage. These burns require immediate medical attention.

6.2. Arc burns:

Arc burns or flash burns are the result of high temperatures in close proximity to the body and are produced by an electric are or explosion. These burns should be treated promptly.

6.3. Thermal contact burns:

Thermal contact burns are those normally experienced when the skin comes in contact with hot surfaces of overheated electrical conductors, conduits, or other energised equipment. Additionally, clothing may be ignited in an electrical accident and the thermal burn will result. It may be remembered here that sometimes, all three types of burns may be produced simultaneously. Electric shock can also cause bruises, bone fractures, and even death resulting from collisions or falls. In some cases, injuries caused by electric shock can be a contributory cause of delayed fatalities.

6.4. Type of burns from shock

Surface Burns : It can be caused by:
– Entrance and exit of electrical current through the body.
– A very small amount of current.
– 1st degree to 3rd degree burns.
Internal Tissue Burns: It can be caused by:
– Current flowing through organs of the body.
– Current in excess of 1.5 amps.
– 4th degree (internal) burns.
– Internal organs.
– Typically fatal.

7. What to do in case of electrical shock?

You are aware that the electricity will follow any available path. Electricity travels at the speed of light. At 299800 Km per second, you are not given the slightest warring: there is no time to react. The rescue of electrical shock victims depend on prompt action.

In case of electrical shock, the following steps are to be taken immediately:
– Shut off the voltage at once.
– Do not make direct contact with any part of the victim’s body with any part of your body.
– Try to free the victim from live conductor by using a dry piece of wood or dry plastic or wooden broom or dry clothing or other non conducting material.
– Determine the victim is breathing.
– If the victim is not breathing, apply cardiopulmonary resus citation (CPR) and First- Aid without any delay
In case of electrical shock, the following First – Aid should be given to the victim:
– Cool the burn with running water.
– Cover the victim with a blanket.
– Do not attempt to remove burned clothing.
– Do not apply ice or any other ointment or cotton dressing to the burn.
– Handle the victim with care.
– Keep the victim from moving.
– Treat for shock.
– Maintain body temperature.
– Do not give anything by month.
– Call for emergency medical attention.

8. Fires due to short circuit

In addition to shock and burn hazards, electricity poses other dangers too. For example, arcs that results from short circuits can cause injury or start a fire. Extremely high energy arcs can damage equipment, causing fragmented metal to fly in all directions. Even low energy arcs can cause violent explosions in atmospheres that contain flammable gases, vapours, or combustible dusts. Electricity can cause fire in a number of ways, and some of the situations can be:

Over heating of conductors and cables due to over loading
Over heating of flammable materials placed too close to electrical equipment
Ignition of flammable materials as a result of arcing or the scattering of hot particles as a result of an electrical fault.
Current leaking to earth or between conductors due to low levels of insulation resistance.

Injuries due to fire are usually burns, but may also be as a result of inhalation of smoke. Injury from arcs may also be as a result of burning from the arc. Arc burns are usually very severe and are often fatal. Electrical equipments such as motors, cables, may explode violently when they are subjected to much higher levels of current than they are designed to carry.

9. Circuit protection devices

Fuses, circuit breakers and ground – fault circuit interrupters are three well – known circuit protection devices used to prevent electrical hazards. Many are designed to automatically limit or shut off flow of electricity in the event of a ground fault, overload, or short circuit in the wiring system. Fuses and circuit breakers prevent over – heating of wires and components. They disconnect the circuit when it becomes overloaded. The best way to reduce the risk of death from electric shock at home is to have a safety switch, called a Residual Current Device (RCD) or Ground Fault Circuit Interrupter (GFCI), fitted within your household fuse box. If there is faulty or wet wiring, or any electric current passing through person, the safety switch will cut off the power within a fraction of a second.

The RCD or GFCI is designed to shutoff electric power, if a ground fault is detected. The RCD or GFCI is useful near sinks and wet locations. However, they may not be useful for certain apparatus as they can cause equipment to shutdown unexpectedly. Though the safety switch is not guaranteed to stop an electrical shock, it is guaranteed to make the injury much less serious. Series – wound motor are casually found in appliances such as mixers, blenders, and vacuum cleaners, power drills, vacuum pumps, rotary evaporators and stirrers. These appliances should not be used unless flammable vapours are adequately controlled.

10. Unsafe conditions and unsafe practices

Majority of the Electrical accidents are caused by a combination of three factors:

Unsafe equipment and / or installation.
Unsafe workplace made by the environment.
Unsafe work practices.

UNSAFE CONDITIONS AND PRACTICES LEADING TO POTENTIAL ELECTRICAL HAZARDS

While conducting safety audits in various production facilities and residential building, the author had come across numerous locations where unsafe conditions and unsafe practices were followed by the employees and occupants, which could have lead to potential electrical hazards. Selected photographs highlighting unsafe conditions and unsafe practices which were observed by the author during the safety audits are exhibited (1 to 10) here for the benefit of readers.

It may be seen from these exhibits that unsafe conditions were prevailed in many houses and work places. Similarly, many of us, one way or other neglect safe practices which could end up in many electrical accidents. Safe conditions and safe practices are a prerequisite for reducing electrical accidents. With this in view some of the Do’s and Don’ts for working with electricity are given below:

Do’s for working with electricity:

Always wear rubber soled shoes and safety gloves when working with electricity
Use double insulated tools.
Use rubber floor mating if possible
Utilize nonconductive tools and ladders
Use only THREE pin plugs, which provide a path to ground that helps prevent the built up or voltages that may result in an electrical shock or spark.
Use shut off switches and / or circuit breakers to shut off equipment in the event of fire or electrocution
Always use ground fault circuit interrupters around areas where there is water
Keep combustible materials away from lamps or heating devices.
Live parts of electrical equipments must be guarded against accidental contact
Limit the use of extension cords or multiple adapters
Inspect the wiring of equipment before each use
Switch off lamps when changing light bulbs.
Disconnect appliances before cleaning.
Call the fire station in case of an electrical fire.
Call the electricity office, if you see person has been electrocuted.
Before you work on a rooftop television antenna, make sure the area is clear of power lines.
Install antennas where they won’t touch or fall on electric lines.
If a cord or plug is warm or hot to touch, unplug it immediately, check wires, extension cords and appliances for signs of wearing.
In case of an electrical fire, if you are safe, unplug the appliance and use DCP type fire extinguisher to douse the flames.
Stay in the car during a storm because the rubber tires stop electricity from passing through it, if the car is struck by lightning or fallen cable.

Don’ts for working with electricity:

Do not plug electrical appliances in bathroom unless specific safety devices have been installed.
If you are in contact with water never touch electrical light switch.
Do not put your fingers in a light bulb holder.
Do not put any into an outlet except a plug.’
Do not leave electric devices where small children may have access.
Do not use a lamp in a metal holder fixed to the end of a loose flexible wire as a portable hand lamp.
Never climb transmission towers.
Don’t attempt to fix cord that have been cut or damaged.
Never use damaged cords.
Never pull out a plug by the cord.
Never place electrical cords under carpets which can result in wearing of the cord.
Never bend or remove the ground on a three pin plug, which is designed to help prevent shock and may save your life.
Do not use extension cords as permanent wiring as they are not designed for it.
Never use cords or plugs that show wear or damage, they can cause shock or fires.
Do not overload an extension cord.
Never puncture insulation of electrical cords by nailing them to any substances.
While climbing trees stay away from those near power lines.

11. Statutory provisions

As per Section 29 of the Indian Electricity Rules 1956, all electric supply lines and apparatus shall be of sufficient ratings for powers, insulation and estimated fault current and of sufficient mechanical strength, for the work they may be required to do and shall be constructed, installed, protected, worked, and maintained in such a manner as to ensure safety of personnel and property.

This provision covers all the aspects for ensuring safety right from choosing of materials for electrical installation, actual installation, protective devices to be provided, tests to be taken, periodical maintenance and upkeep, etc. In fact there are specific rules elsewhere in the Electricity Rules, specifying requirements in connection with the various aspects mentioned above. But where no such specific rules exit this provision can be made applicable to ensure general safety. While choosing materials for the electrical installation it is always desirable to go in for materials manufactured to the specifications of Bureau of Indian Standards.

12. Conclusion

Human error is the most probable cause of electrocution. Many fire hazards in the home and work places are caused by electrical overloads and faulty electrical appliances. Electricity is the most dangerous hazards within the home. Forgetting to turn off an electrical appliance, such as an oven, water heater can create a potential hazard in your home. Mind you, even the current in a light bulb, found inside your fridge, is enough to kill you. Sizes of cables, capacities and ratings of motors, transformers and other electrical apparatus, switches and circuit breakers shall be determined with reference to the load which they are going to carry and voltage drop considerations.

Grades of insulating material should also be decided with reference to the locations where these things are going to be installed i.e. the temperature conditions, moisture, presence of inflammable gases, chemical fumes, etc. Cheaper and sub-standard materials should be avoided as they fail within a short time. The layout of electrical installation should be planned and designed in such a way that the appearance will not only be decent and tidy but also will be easy to maintain and inspect, during the course of time. Provisions of various rules laid down should also be complied with to ensure safety. Work should be got executed through licensed electrical contractors under the supervision of competency certificate holder.

Periodical cleaning of contacts, replacements, insulation tests of wiring installation, windings of motors and other insulated electrical appliances, earth continuity and earth resistance tests should be carried out as per rules or national codes / standards and steps should be taken to maintain the quality of the respective items. A record of such tests should be maintained. Fuses, operating devices and relays should be checked periodically for proper operations.

References :

American Welding Society – Electrical hazards (Safety and Health Fact sheet No. 5.) 2006
India, Ministry of Home Affairs – National Crime Records Bureau of India, Annual Report, 2012.
Indian Electricity Rules, 1956.
International Symposium on Electrical Accidents, Paris 1962. Geneva, ILO / CIS , 1964
Nair R. R. – A number of safety audits carried out in various factories and high rise buildings.
Nair R. R. – Electrical hazards – Management of Industrial Hazards (CEP Publication) All India Council for Technical Education, Bangalore, 1998.
National Fire Protection Association (NFPA) – NFPA 70E Standard for electrical safety in the workplace 2004 edition.
Neitzel, Dennis K – The hazards of electricity – Do you know why they are? AVO Training Institute Inc., Texas.
Queensland Department of Justice and Attorney – Electrical safety: Electrical dangers and hazards, 2012.
Trustees of Princeton University-Electrical safety, 2007
U. S. Department of Labour- Occupational Safety and Health Administration (OSHA) –Controlling electrical hazards (OSHA 3075), 2002 (Revised)
U. S. Department of Labour – Occupational Safety and Health Administration (OSHA) – Electrical Standards, Federal Register, 29 (FR 1910 – 1961).

About Author
Mr.R.R.Nair has more than 40 year’s exposure in Occupational Safety, Health & Fire Protection. He is author of 15 books & more than 55 articles in various topics on Safety, Health & Environment. He has carried out more than 50 safety audits in various industries and high rise buildings.
For more information contact:
M.: 09224212544 / 09167246783, Res.: 022 2766 5975
E-mail: [email protected]

Electrical Hazards Mr. R. R. Nair