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1. Waqar Shehbaz
Mechanical Department
UET Peshawar Pakistan

2. Objectives:
• Electrical hazards defined.
• Sources of electrical
hazards.
• Electrical hazards to
humans.
• Detection of electrical
hazards
• Reducing electrical
hazards.
Hazard means:
• Any potential or actual
threat to the wellbeing of
people, machinery or
environment
Typical circuit wiring has
• Hot wire carrying current
• Neutral wire/ grounded
conductor
• Ground wire/ grounding
conductor

3. Major causes of electrical
shocks
Sources of electrical hazards
1. Short circuit hazards.
2. Water contacts.
3. Electrostatic hazards.
4. Arcs and sparks hazards
5. Combustible and
Explosive Material.
6. Lightening Hazards.
7. Improper wiring
• Jump of the ground wire
• OPEN GROUND WIRE
• REVERSE POLARITY
Type of
resistance
Resistance in Ohms
Dry skin 100,000 to 600,000 Ohms
Wet skin 1,000 Ohms

4. Shock depends upon
1. Skin resistance
2. Skin moisture
Electrical severity depend
upon
1. Dosage of current
2. Path of current
3. Length of time a person is
subjected to the current
Shock/Level of Current
1. Freeze
2. Let Go Current
Shock Effects
1. Stoppage of heart & breathing
2. Severe bleeding
3. Burns
4. Muscles clamping
5. Consciousness

5. Effects
1. No sensation
2. Reflex reaction to jump away
3. Painful shock
4. Let go current for female & male respectively
5. Local muscle contraction, freezing for 2.5% pop
6. Local muscle contraction, freezing for 50% pop
7. Respiratory failure, death if prolong >3min
8. Ventricular fibrillation & death
9. Heart & respiratory failure, unconsciousness, burns
to skin & internal tissues, death
Current(milli Amp)
1. Less than 1
2. 1
3. More than 3
4. 6 & 9
5. 10-15
6. 30-50
7. 50-100
8. 100-200
9. Over 200
Circuit
Tester
Receptacle
Tester
Continuity
Tester
Detection Of
Electrical
Hazard

6. Lightning Hazard Control:
Various methods of reducing the risk of
electrocution by lightning.
 Avoid standing in high places or near tall
objects.
 Do not work with flammable liquids or
gases during electrical storms.
 Ensure proper grounding of all electrical
equipment.
 If in a metal building, stay inside the
building and do not touch the walls.
 Wear rubber clothing if outdoor.
 Do not work touching or near conducting
materials especially those in contact with
earth like fences.
 Avoid using the telephone during an
electrical storm.
 Do not use electrical equipment during the
storm.
 Avoid standing near open doors or
Techniques to reduce the
hazards:
Electrical System Grounding:
Bonding:
Separate Equipment Grounding:
Ground Fault Interrupter:
Fuse:
Magnetic Circuit Breaker:
Thermal circuit Breakers:
Double Insulation:
Interlock: