29 CFR 1926.400; Subpart K29 CFR 1926.400; Subpart KNational Electric Code (NEC)National Electric Code (NEC)

Electricity is the Electricity is the second leading second leading cause of deathcause of death in construction. in construction.

Electrocutions make up 12% of Electrocutions make up 12% of construction fatalities annually.construction fatalities annually.

Over 30,000 non-fatal shocks Over 30,000 non-fatal shocks occur each year.occur each year.

Over 600 deaths occur annually Over 600 deaths occur annually due to electrocution. due to electrocution.

Source: Bureau of Labor Statistics

Leading Causes of Electrical Leading Causes of Electrical Accidents:Accidents:Drilling and cutting through cablesDrilling and cutting through cablesUsing defective tools, cables and Using defective tools, cables and

equipmentequipmentFailure to maintain clearance distance Failure to maintain clearance distance

of 10 feetof 10 feetFailure to de-energize circuits and Failure to de-energize circuits and

follow Lockout/Tagout proceduresfollow Lockout/Tagout proceduresFailure to guard live parts from Failure to guard live parts from

accidental worker contactaccidental worker contact

Leading Causes of Electrical Leading Causes of Electrical Accidents:Accidents:Unqualified employees working with Unqualified employees working with

electricityelectricityImproper installation/use of temporary Improper installation/use of temporary

electrical systems and equipmentelectrical systems and equipmentBy-passing electrical protective devicesBy-passing electrical protective devicesNot using GFCI (ground fault circuit Not using GFCI (ground fault circuit

interrupters) devicesinterrupters) devicesMissing ground prongs on extension cordsMissing ground prongs on extension cords

ShockShock – Most common and can cause electrocution – Most common and can cause electrocution or muscle contraction leading to secondary injury or muscle contraction leading to secondary injury which includes fallswhich includes falls

FiresFires – Enough heat or sparks can ignite combustible – Enough heat or sparks can ignite combustible materialsmaterials

ExplosionsExplosions – Electrical spark can ignite vapors in the – Electrical spark can ignite vapors in the airair

Arc Flash Arc Flash - can cause burns ranging from 14,000 can cause burns ranging from 14,000 degrees f. to 35,000 degrees fdegrees f. to 35,000 degrees f

Arc Blast Arc Blast – In a short circuit event copper can In a short circuit event copper can expand 67,000 times. The expansion causes a expand 67,000 times. The expansion causes a pressure wave. Air also expands adding to the pressure wave. Air also expands adding to the pressure wavepressure wave

Current = Flow RateCurrent = Flow RateExample – 15 gallons per minute Example – 15 gallons per minute

Resistance = Diameter of HoseResistance = Diameter of HoseExample – Larger hose (less resistance), Example – Larger hose (less resistance), more water flowsmore water flows

Voltage = Water PressureVoltage = Water PressureExample – 45 PSIExample – 45 PSI

Flow of WaterFlow of Water

Electrical Electrical currentcurrent is the flow of is the flow of electrons through a conductor.electrons through a conductor.

A A conductorconductor is a material that is a material that allows electrons to flow through it.allows electrons to flow through it.

An An insulatorinsulator resists the flow of resists the flow of electrons.electrons.

ResistanceResistance opposes electron flow. opposes electron flow.

Circuits are AC Circuits are AC (alternating current) or (alternating current) or DC (direct current).DC (direct current).

Current is usually AC.Current is usually AC.

AC current has five AC current has five parts:parts:

(1) Electrical source(1) Electrical source(2) HOT wire to the (2) HOT wire to the

tool.tool.(3) The tool itself(3) The tool itself(4) NEUTRAL wire (4) NEUTRAL wire

returns electricity returns electricity from the toolfrom the tool

(5) GROUND (5) GROUND

Current travels in Current travels in closed circuits closed circuits through conductorsthrough conductors (water, metal, (water, metal, the human body).the human body).

Shock occurs when the Shock occurs when the body body becomes a part of the circuit.becomes a part of the circuit.

Current enters at one point & leaves Current enters at one point & leaves at another.at another.

Contact with both Contact with both conductorsconductors

Contact with one Contact with one conductor and conductor and groundground

With a tool: contact With a tool: contact with “hot” metal with “hot” metal part and ground part and ground (1), (2) & (3)(1), (2) & (3)

Severity of the Shock depends on:Severity of the Shock depends on:Amount of current Amount of current

Determined by voltage and resistance to Determined by voltage and resistance to flowflow

Path through the bodyPath through the bodyDuration of flow through the bodyDuration of flow through the bodyOther factors such as general health Other factors such as general health

and individual differences.and individual differences.

Luling, La. - A man was electrocuted when his Luling, La. - A man was electrocuted when his sweat dripped into the electric drill he was using sweat dripped into the electric drill he was using to build a swing set in his backyard, the coroner to build a swing set in his backyard, the coroner said.said.

Richard Miller was pronounced dead Sunday at St. Richard Miller was pronounced dead Sunday at St. Charles Hospital, said David Vial, St. Charles Charles Hospital, said David Vial, St. Charles Parish coroner. Miller, 54, had been using an Parish coroner. Miller, 54, had been using an electric drill in 90 degree heat, Vial said Monday.electric drill in 90 degree heat, Vial said Monday.

““Apparently the man was sweating profusely,” Vial Apparently the man was sweating profusely,” Vial said. “He probably was pushing against the drill said. “He probably was pushing against the drill with his chest and his perspiration went into the with his chest and his perspiration went into the drill itself and made a contact.”drill itself and made a contact.”

The Associated PressThe Associated Press

AC current (mA) Effect on human body

1 Slight tingling sensation

2-9 Small shock

10-24 Muscles contract causing you to freeze

25-74 Respiratory muscles can become paralysed; pain; exit burns often visible

75-300 Usually fatal; ventricular fibrillation; entry & exit wounds visible

>300 Death almost certain; if survive will have badly burnt organs and probably require amputations

Using a 120 volt circuit and resistance for Using a 120 volt circuit and resistance for wet & dry skin:wet & dry skin:

E=IRE=IR: Voltage=Current x Resistance: Voltage=Current x Resistance (Volts) (Amps) (Ohms)(Volts) (Amps) (Ohms)

So: So: I=E/RI=E/R

Dry Skin =120/100,000=.0012 ampsDry Skin =120/100,000=.0012 amps ==1.2ma1.2ma flowing through flowing through body to groundbody to ground

Wet skin =120/1000=.120 ampsWet skin =120/1000=.120 amps ==120ma120ma flowing through flowing through body to ground body to ground

RememberRemember: : 1 Amp = 1000 milliamps1 Amp = 1000 milliamps

Effects of Current FlowEffects of Current Flow

If you come across a person receiving an electric shock:

if possible, disconnect the electrical supply (switch?)

assess the situation – never put yourself at risk

take precautions to protect yourself and anyone else in the vicinity

apply the first aid principles (e.g. DRSABCD)

assess the injuries and move the casualty to a safe area if required

administer first aid if trained

seek urgent medical attention

You could be the victim if you:

don’t follow proper procedures around electricity

use electrical equipment improperly

use faulty electrical equipment

Electricity is invisible – this in itself makes it dangerous

It has great potential to seriously injure or kill

Everyone is exposed to electrical hazards, not just electricians

Employers must follow the OSHA Employers must follow the OSHA Electrical Standards (Subpart K)Electrical Standards (Subpart K)

Electrical installationElectrical installationSubpart K includes four proactive Subpart K includes four proactive

methods:methods:Electrical IsolationElectrical IsolationEquipment GroundingEquipment GroundingCircuit InterruptionCircuit InterruptionSafe Work PracticesSafe Work Practices

We can be safe by keeping We can be safe by keeping electricity away from us. We can:electricity away from us. We can:InsulateInsulate the conductors.the conductors.

Example: The insulation on extension Example: The insulation on extension cords.cords.

ElevateElevate the conductors.the conductors.Example: Overhead powerlines.Example: Overhead powerlines.

Guard Guard the conductors by enclosing the conductors by enclosing them.them.Example: Receptacle covers, boxes, & Example: Receptacle covers, boxes, &

conduitconduit..

The first way to safeguard workers from The first way to safeguard workers from electrically energized wires is through electrically energized wires is through insulationinsulation..

Rubber and plastic is put on wires to prevent Rubber and plastic is put on wires to prevent shock, fires, short circuits and for strain shock, fires, short circuits and for strain relief.relief.

It is always necessary to check the insulation It is always necessary to check the insulation on equipment and cords before plugging on equipment and cords before plugging them in.them in.

Remember, even the smallest defect will Remember, even the smallest defect will allow leakage!allow leakage!

Defective Extension CordsDefective Extension Cords

Worker attempted to Worker attempted to climb scaffold with climb scaffold with electric drill.electric drill.

Drill’s cord was Drill’s cord was damaged with bare damaged with bare wires showing.wires showing.

The bare wire The bare wire contacted the contacted the scaffolding.scaffolding.

The worker died!The worker died!

Remember, never allow yourself, Remember, never allow yourself, your tools, or the materials you are your tools, or the materials you are working with to be within working with to be within 10 feet10 feet of of energized lines!energized lines!

Clearance of worker and any equipment, Clearance of worker and any equipment, tools, materials, or scaffold near tools, materials, or scaffold near uninsulated lines is 10 feet!uninsulated lines is 10 feet!

A worker was A worker was attempting to attempting to move mobile move mobile scaffold.scaffold.

Scaffold made Scaffold made contact with 7200 contact with 7200 volt line.volt line.

The worker died.The worker died.

The third way to safeguard workers The third way to safeguard workers from electrically energized wires is by from electrically energized wires is by guardingguarding them.them.

Covers, boxes, and enclosures are Covers, boxes, and enclosures are often put around conductors to often put around conductors to prevent worker contact.prevent worker contact.

It is always necessary to check that It is always necessary to check that electrical boxes and panels are electrical boxes and panels are covered and free from missing “knock-covered and free from missing “knock-outs”. outs”.

Remember, electric equipment Remember, electric equipment operating at 50 volts or more must be operating at 50 volts or more must be guarded!guarded!

Guarding the ConductorsGuarding the Conductors

Guarding the ConductorsGuarding the Conductors

We can be safe by providing a We can be safe by providing a separate, low resistance separate, low resistance pathwaypathway for electricity when it for electricity when it does not follow normal flow does not follow normal flow (ground prong).(ground prong).

GroundingGrounding gives the stray gives the stray current somewhere to go and current somewhere to go and keeps you from becoming part keeps you from becoming part of the circuit.of the circuit.

Grounding Grounding will not workwill not work if the if the electricity can flow through you electricity can flow through you more easily than the ground. This more easily than the ground. This can happen when:can happen when:

Your tool doesn’t have a ground pin.Your tool doesn’t have a ground pin.You’re working in wet locations.You’re working in wet locations.You’re touching a metal object.You’re touching a metal object.

All circuits and All circuits and extension cords. extension cords.

All noncurrent All noncurrent carrying metal parts.carrying metal parts.

Portable & semi-Portable & semi-portable tools and portable tools and equipment unless equipment unless double insulated.double insulated.

Do Not Eliminate the Ground!Do Not Eliminate the Ground!

You become the next-best path for current!You become the next-best path for current!

Do Not Reverse PolarityDo Not Reverse Polarity

The prongs are different The prongs are different sized so you can’t turnsized so you can’t turnthe plug around. If youthe plug around. If youdo, the electrical fieldsdo, the electrical fieldswithin the motor are alwayswithin the motor are alwaysenergized. If there isenergized. If there ismoisture present, the case moisture present, the case is likely to be “hot”. Evenis likely to be “hot”. Evenwith double-insulated tools, with double-insulated tools, you still could get a shock. you still could get a shock.

We can be safer by automatically We can be safer by automatically shutting off the flow of electricity in shutting off the flow of electricity in the event of leakage, overload, or the event of leakage, overload, or short circuit. short circuit.

Ground Fault Circuit Interrupters Ground Fault Circuit Interrupters (GFCI) are circuit protection (or (GFCI) are circuit protection (or “overcurrent”) devices that protect “overcurrent”) devices that protect you, the worker.you, the worker.

Circuit breakers & fuses protect Circuit breakers & fuses protect equipmentequipment, not you, because they , not you, because they take too much current & too much take too much current & too much time to trip.time to trip.

Circuit Breakers and FusesCircuit Breakers and FusesOnlyOnly protect the building, protect the building,

equipment, and toolsequipment, and tools from heat from heat build-up!build-up!

Never depend on circuit Never depend on circuit breakers or fuses to prevent breakers or fuses to prevent shocks!shocks!

Ground Fault Circuit Ground Fault Circuit InterrupterInterrupter (GFCI) (GFCI)Is the only device which willIs the only device which will

protect the workerprotect the worker from shock from shock and electrocution!and electrocution!

The GFCI detectsThe GFCI detects‘‘leakage’ of 4-6leakage’ of 4-6milliamps & opensmilliamps & opensthe circuit in 1/40the circuit in 1/40thth

of a second. of a second.

It It willwill work without work withoutthe ground plugthe ground plugbut but not not fast fastenough if enough if youyou are are the ground . the ground .

Permanent Equipment in Temporary UsePermanent Equipment in Temporary Use

What is wrong with using this as a ‘splitter’?What is wrong with using this as a ‘splitter’?

Must be in Must be in good shape without splices.good shape without splices.Cannot be secured with staples, nails Cannot be secured with staples, nails

or bare wire.or bare wire.Must be protected from damage.Must be protected from damage.Must have a ground pin.Must have a ground pin.Should be inspected regularly and Should be inspected regularly and

pulled from service if defective.pulled from service if defective.Cannot be repaired with electrical or Cannot be repaired with electrical or

duct tape. Must repair with heat-duct tape. Must repair with heat-shrink sleeve or bonding/vulcanizing shrink sleeve or bonding/vulcanizing tape to retain original insulation tape to retain original insulation properties.properties.

Extension Cords-What’s the Difference?Extension Cords-What’s the Difference?

Clever Or Foolish?Clever Or Foolish?

No metal ladders for or near No metal ladders for or near electrical work.electrical work.

No wet hands when plugging No wet hands when plugging or unplugging or unplugging cords/equipment.cords/equipment.

No raising or lowering tools No raising or lowering tools by the cord.by the cord.

Unless equipment is designed Unless equipment is designed for it, cannot be used in damp for it, cannot be used in damp and wet locations.and wet locations.

Photo depicts hazardous conditionPhoto depicts hazardous condition

Inadequate wiringInadequate wiringExposed electrical partsExposed electrical partsWires with bad insulationWires with bad insulationOverloaded circuitsOverloaded circuitsDamaged power tools and Damaged power tools and

equipmentequipmentUsing the wrong PPE and toolsUsing the wrong PPE and toolsOverhead power linesOverhead power linesDamaged extension cordsDamaged extension cords