Effects of Electricity on Human Body

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Effects of Electricity on Human BodyWe need to be knowledgeable and aware about electrical safety;

else, life may be the price to pay

Why worry about electricity?

-Electrocution is an extremely dangerous scenario wherein thehuman body experience a lethal amount of electrical energy.

-Electrocutions rank f o u r t h in causes of industrial fatalities (behindtraffic, violence and construction). It is estimated that 600 peopledie every year of electrical causes. Most of these accidents involvelow voltage (600 volts or less).

Causes of Industrial Fatalities

SOURCE: Bureau of Labor Statistics, 2012

Traffic

41%

Violence17%

Construction16%

Electrocution15%

Contact withobjects

7%

Fires &Explosions

3%

Others1%

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Electricity flowing through the human body can shock, cause involuntary musclereaction, paralyze muscles, burn tissues and organs or kill. In case of electric shock, the

amount of current flow through the body and the corresponding body sensation areidentified in the following graph.

Electric Shock VS Body Sensation

Current FlowThrough the Body

in Amperes

Body Sensation

1.00.5 Severe burns

Breathing stops0.2 DEATH

0.1Very difficult breathing

Labored breathingSevere shock

0.05Paralysis

Cannot releasePainful sensation

0.02 Mild sensation0.01

0.005 Slight sensation0.0020.001

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A small night-light with a 6-watt bulb draws 0.05 ampere, and even that smallamount of current can be fatal. Here are some effects of current (in milli amps) passingthrough a 150 pound body (note that perception is only 0.5 to 1.5 milli amps):Current passing through your body can cause electric shock, resulting in 3 types ofpotential injuries:

1. Burns (arcs burns with heat and radiation)2. Physical injuries (broken bones, falls, and muscle damage)

-at 10 milli amps, the muscles clamp on to whatever the person is holding.3. Nervous System Effects (stop breathing at 30 to 75 milli amps alternating current

at 60 Hz, fibrillation at 75 to 100 milli amps at 60 Hz)

Fibrillation - heart is twitching and there is no blood flow to the body. The heart can bedamaged because it is in the path of the most common routes electricity will takethrough the body: hand to hand, hand to foot.

Electricity is an integra l part of todays modern world, and sometimes it is easy to forget just how dangerous it can be. Given the correct circumstances, it can kill. But it can alsoshock you painfully, damage sensitive equipment, and ignite combustible materials.

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Effects can range from a barely perceptible tingle to severe burns and immediatecardiac arrest. Although it is not known the exact injuries that result from any givenamperage, the following table demonstrates this general relationship for a 60-cycle,hand-to-foot shock of one second's duration:

Wet conditions are common during low-voltage electrocutions. Under dryconditions, human skin is very resistant. Wet skin dramatically drops the body'sresistance.

Dry Conditions:Current = Volts/Ohms = 120/100,000 = 1mAa barely perceptible level of current

Wet conditions:Current = Volts/Ohms = 120/1,000 = 120mA sufficient current to cause ventricular

fibrillation

If the extensor muscles are excited by the shock, the person may be thrownaway from the circuit. Often, this can result in a fall from elevation that kills avictim even when electrocution does not.

When muscular contraction caused by stimulation does not allow the victim tofree himself from the circuit, even relatively low voltages can be extremelydangerous, because the degree of injury increases with the length of time thebody is in the circuit.

LOW VOLTAGE DOES NOT IMPLY LOW HAZARD!

100mA for 3 seconds = 900mA for .03 seconds in causing fibrillation

Note that a difference of less than 100 milliamperes exists between a current thatis barely perceptible and one that can kill.

High voltage electrical energy greatly reduces the body's resistance by quicklybreaking down human skin. Once the skin is punctured, the lowered resistanceresults in massive current flow.

At 1,000 volts, Current = Volts/Ohms = 1,000/500 = 2 Ampswhich can cause cardiac arrest and serious damage to internal organs.

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ELECTRICAL FATALITY RATES by EVENT

The figure shows that contact with overhead power lines killed more constructionworkers than any other single type of electrical accident from 2003 to 2007, but the datafor this category suggest a sustained decline since 2006. Over the same period, contactwith wiring, transformers, or other electrical components and the contact with electriccurrent of machine, tool, appliance, or light xture fatality rates remained essentiallyunchanged.

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ELECTRICAL FATALITY RATES by EVENT

The figure shows electrical fatality rates in major industry groups. As described earlier,the all -industry curve is produced by dividing the total annual number of electricalfatalities by the total employment. The rates for individual industries are calculatedsimilarly but use employment figures for each industry as the denominator.

These industry groups, construction, professional and business, trade andtransportation, mining, and manufacturing, had electrical fatality rates that wereconsistently above the all-industry average. The construction industry had the highestrate of electrical fatalities each year studied within 2003-2010.

The Construction Industry accounted for 52% of all electrical deaths between 2003-2010.

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FACTS

Between 2003 and 2007, 28,401 workers died while on the job. Contact withsome form of electric current was the seventh leading cause of occupational fatalitiesduring this period, accounting for 1,213 work-related fatalities. Another 13,150 workerswere injured so severely from these electrical accidents that their injuries required timeoff from work.

Construction trades (including electricians, construction laborers, painters,roofers, and carpenters) and installation, maintenance, and repair professionals(including those who install and repair electrical power lines, HVAC, and refrigerationequipment and perform general maintenance and repair work) were recognized as thetop two occupational groups with the most fatal electrical injuries from 2003 to 2007.During this time, construction trade Sacco united for 445 (37%) of total electricalfatalities while another 257 (21%) of these fatal work-related accidents occurred duringinstallation, maintenance, and repair of electrical power lines, HVAC, and refrigerationequipment. A total of 207 (47%) of the victims who worked in construction trades wereelectricians. Another 104 (23%) were construction laborers, 27 (6%) were painters, 26(6%) were roofers, and 24 (6%) of construction trade workers who were victims ofelectrical fatalities from 2003 to 2007 were carpenters. The specific circumstancessurrounding the electrocutions in the remaining 12% of the deaths were not categorizedin these data.

ELECTRIC BURNS A burn that results from electricity passing through thebody causing rapid injury. Approximately 1,000 deathsper year in the country due to electrical injuries arereported.

Although a current may not pass through vitalorgans or nerve centers, internal electrical burns can stilloccur. These burns, which are a result of heat generated

by current flowing in tissues, can be either at the skin surface or in deeper layers(muscles, bones, etc.) or both. Typically, tissues damaged from this type of electricityburn heal slowly.

Burns caused by electric arcs are similar to burns from high temperaturesources. The temperature of an electric arc, which is in the range of 4,000 - 35,000 ,can melt all known materials, vaporize metal in close proximity, and burn flesh andignite clothing at distances up to 10 ft. from the arc. Damage to internal tissues may notbe apparent immediately after contact with the current. Internal tissue swelling andedema are also possible

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CRITICAL PATH OF ELECTRICITY

Current flowing from

one hand to the other

Current flowing fromone hand to the other

Current flowing fromthe head to either foot

When this happens, it paralyzes the respiratory or heart muscles,initiating ventricular fibrillation, and/or burning vital organs

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TYPES OF BURNS(ACCORDING TO DEGREE)

Type Layers

involved Appearance Texture Sensation Healing

TimePrognosis

Superficial(First

degree ) Epidermis Red withoutblisters Dry Painful 5 10 days

Heals well;Repeatedsunburns

increase the riskof skin

cancer later in lifeSuperficial

partialthickness(Seconddegree )

Extendsinto

superficial(papillary)

dermis

Redness withclear blister.

Blanches withpressure.

Moist Very painful less than 2 3 weeks

Local infection/cellulitis but no

scarring typically

Deep partialthickness(Seconddegree )

Extendsinto deep(reticular)

dermis

Yellow orwhite. Lessblanching.

May beblistering.

Fairly dryPressure

anddiscomfort

3 8 weeks

Scarring,contractures(may require

excision and skingrafting)

Fullthickness

(Thirddegree )

Extendsthroughentire

dermis

Stiff andwhite/brown

No blanchingLeathery Painless

Prolonged(months)

andincomplete

Scarring,contractures,

amputation (earlyexcision

recommended)

Fourthdegree

Extends

throughentire skin,

and intounderlyingfat, muscleand bone

Black;charred

with escharDry Painless Requiresexcision

Amputation,significantfunctional

impairment and,in some cases,

death.

The effects of electric current on the human body can vary depending on the following: Source characteristics-current, frequency and voltage of all electric energy

sources.

Body impedance and the currents pathway through the body. How environmental conditions affect the bodys contact resistance. Duration of the contact.

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SIX CATEGORIES OFELECTRICAL BURNS

Electrical burns can be classified into six categories, and any combination of thesecategories may be present on an electrical burn victim:

Low-voltage burn . A burn produced by contact with a power source of 500 voltsor less is classified as a low-voltage burn. The current at this voltage is notenough to cause tissue damage along its path except at the contact site.

High voltage burn . This burn is very severe as the victim makes direct contactwith the high voltage supply and the damage runs its course throughout the body

Arc burn . This type of burn occurs when electrical energy passes from a high-resistance area to a low-resistance area. No contact is required with an arc burnas the electricity ionizes air particles to complete the circuit.

Flash burn . Flash burns are caused by electrical arcs that pass over the skin.The intense heat and light of an arc flash can cause severe burns. Although theburns on the skin are largely superficial and cover a large area, tissues beneaththe skin are generally undamaged and unaffected.

Flame burn . Associated with flash and arc burns, flame burns are caused bycontact to objects that were ignited by an electrical source.

Oral burns . This is caused by biting or sucking on electrical cords, and it mostcommonly happens to children. Electrical current typically passes from one sideof the childs mouth to the other, possibly causing deformity.

Low-Voltage burn

High-voltage burn

Arc burn

Flash burn

Flame burn

Oral burn

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HOW TO TREAT...

MAJOR BURNS

1Do not touch the victim unless it is safeto do so, to avoid being burned yourself.

Make sure that the source of electricity has been

shut off and safely unplugged.

If it is not immediately possible to shut off the

power, move the victim away from the source with a

non-conductive item, like a stick or blanket.

Check the area to ensure your safety.

2Call for immediate medicalassistance .

3Check the victim for breathing and apulse. If necessary -- meaning, if theperson is not breathing, perform rescuebreathing and CPR.

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4Check the victim for symptoms

of shock. They may be cold, withclammy skin, a pale appearance and arapid pulse.

5Treat the burned area(s) untilmedical assistance arrives.

Cover the burns with a dry, sterile

bandage only. For severe burns, do

not attempt to remove pieces of

clothing which have stuck to the skin.

Do not attempt to cool the burns withwater or ice.

Do not apply grease or oil to the

burns.

6Keep the victim warm. Do not allowthem to feel chilly.

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MINOR BURNS

1Hold the burned area undercold, running water, or soakit for about 10 minutes. Makesure not to use ice to cool theburn, as ice can cause furtherdamage to the skin.

Afterwards, carefully wash theaffected area with soap andwater, then gently pat dry.

2Loosely cover the burnedskin with cleanbandage. Change thebandage every so often toprevent any infections on thewounds. Also, avoid wrappingthe area too tightly or youmight risk doing furtherdamage to the burn.

3Take over-the-counter painrelievers such asacetaminophen or ibuprofento soothe the painsymptoms.

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STATIC ELECTRICITYH o w i t c a n d o h a r m ?

Why minimize static shocks?You may be injured by the reaction to the shock even though the shocks are not

hazardous!

What you can do?1. Never clean the glass face of your computer monitor while the computer is

on.

2. During normal operation, the glass surface of a monitors CRT accumulatesan electrostatic charge. When you touch the screen with a finger, the chargein the portion of the screen you touched discharges through your finger with atiny spark. Electric current does not normally flow through glass so only partof the screen that your finger touches is discharged. When you clean amonitor however, the entire glass is wet and the charge on the entire screenwill discharge to your finger or hand, causing a much more painful shock.Clean your monitor before you turn on your computer.

3. Never allow any electrical powered office equipment to become wet while it isturned on.

4. Never turn on any electronic equipment when it is wet.

5. Even when a computer has been turned off for a few minutes, it is best not totouch the monitors CRT while handling or using other electrical/ electronicequipment, including the telephone. Wet or dry, you may receive an electricshock. This shock is similar to the shock you receive when you touch a doorknob after walking across a carpet. Although painful, this type of shock is not

hazardous. However, you may be injured by the reaction to the shock, suchas pulling your hand rapidly away and hitting your elbow against a wall orcabinet.

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CASE STUDY

Explosion during cleaning a tank in Paint Manufacturing Factory

On January 30th, 1995.

An explosion occurred on cleaning a tank in apaint factory. Cleaning was done to changethe contents of the tank. Ethyl acetate wasput in three days after the paint wasremoved.

The tank was left for three days withoutcleaning, and it was scrubbed with a brushhaving a long handle. The ethyl acetate vaporexploded due to static electricity generatedby brushing. One worker received a burn onthe face. Usually, cleaning was carried out

just after drawing-off. Three days passed thistime, and the paint solidified. Then, brushing was done many times. The accidenthappened because a static electricity spark was generated in a combustible solventenvironment. Sufficient management of static electricity was necessary for this cleaningoperation which was highly dangerous.

Eatoneville Static Electricity Discharge

EATONVILLE, Wash. An electrical sparkfrom static electricity destroyed two antiqueplanes, two classic cars and an airplanehangar at Swanson Airfield in Eatonville.the plane's ow ner was draining gas fromone of the planes Friday afternoon into aplastic bucket That's when static electricitycaused a spark, lighting the plane on firethe fire spread to another vintage plane,and two classic cars inside the hangar.

Hudspeth says one of the planes had acloth skin that cover the entire plane andremoved before the owner drain the gas.