An overview of electrical safety in general and in hospital specifically which is a part of safety in biomedical engineering.

1. Electrical
Safety
2022
Sana’a
UST
Presented by:
Shaima Mohammed
Malak Ayman
Under supervision of:
Dr.Mahmoud Al-Rumaima

2. Table of contents
Sources &
Causes
Effect &
Risks
Codes &
Standards
First Aid &
Precaution
Classes &
types
05 06
02 03
04
01
Introduction
& Definitions

3. 1.1 Introduction
Electricity is essential to modern life, both at home
and on jobs. Some employees - engineers,
electricians, electronic technicians, and power line
workers, among them - work with electricity directly.

4. a) Electrical Hazard
Dangerous condition such that contact or equipment
failure can result in electric shock, arc-flash burn,
thermal burn or blast. Dangerous event or condition
due to direct or indirect electrical contact with
energized conductor or equipment and from which a
person may sustain electrical injury from shock,
damage to workplace environment, damage to
property or both.
1.2 Definitions:
b) Electric shock
An electric shock is the effect of an electric current
flowing through the human body.

5. Electrocution results when a person is exposed to a
lethal amount of electrical energy. The term
“electrocution” is death by an electric shock.
Electrocution is the cause of 12% of all workplace
death among young workers. Another statistics
showed that 8.9% of construction worker deaths in
2013 were caused by electrocution. According to the
Bureau of Labor Statistics (BLS), there were more
electrical fatalities in construction than any other
industrial sector. A total of 86 electrical fatalities in
construction occurred in 2018.
c) Electrocution:

6. Common electrical
hazard symbols
2.1 Sources of Electrical
hazards
• Exposed electrical parts
• Overload circuits
• Defective insulation
• Improper grounding
• Damaged power tools
• Overload power lines
• Wet conditions
2. Sources

7. How the electrical shock happen ?
2.2 Causes
An electrical shock, arc flash or arc blast can
occur and a current can go through the body,
due to the following situations:
• Direct contact with live parts of the
installation (exposure to live parts).
• Contact with parts that normally are not live,
but as a consequence of a fault become live
accidentally (indirect contact).
• Existence of potential difference between
different points in the ground.
• The current takes the path of lowest
resistance .

8. The current takes the path
of lowest resistance
2.2
Causes
Electricity takes the
path of least resistance
Live wire contact in one hand

9. The value of the current through the body depends of
the resistance of the skin. This resistance depends of
several factors such as:
2.2 Causes
• Humid or wet skin
• Thickness of the
skin at the contact
point
• Psychological
condition
• Weight
• Sex
• Age

10. The pathway of the current
through the human body is
unpredictable, and pathways
through the heart are the most
dangerous. The figure below
shows possible pathways. Two
points of contact are required on
the body to complete the circuit
for shock current to flow.
2.2 Causes

11. The effects of electrical current through the
human body vary according to:
• The voltage
• The time the current flows
• The value of the current
• The frequency of the network
• The pathway of the current
• The ability of the person to react
3. Effect & Risks
3.1Physiological effect of electricity

12. What is considered safe ?
Electrical installations with voltages
up to 50 V, in dry places, and up to
25V, in wet or humid places (AC)
and up to 120 V in DC are
considered safe in what concerns
direct and indirect contacts.
Increase of frequency decreases
the danger of current through the
human body.
3.1 Physiological effect
of electricity

13. video

14. 3.1 Physiological effect of electricity
What is considered dangerous ?
The called “industrial frequencies” (50 Hz
or 60 Hz) are the more dangerous.
AC or DC, Which one is dangerous ?
Both the AC and DC voltages and
Currents are dangerous & hazardous. But
AC with 50 or 60Hz frequency is more
dangerous than the same voltage of level
for DC.
Effects AC DC
Perception 0.5-1.5 0-4
surprise 1-3 4-15
Reflex Action 3-21 15-88
Muscular Inhibition 21-40 88-160
Respiratory Block 40-100 160-300
Usually Fatal More
than
100
More
than
300

15. Volt or current, Which one is
dangerous ?
Current kills but some amount of voltage
is required to flow current in the body
breaking the human body resistance.
Therefore enough voltage of hundredth
with enough current make electric shock.
Overall, it is mainly the eclectic power (a
mixture of current and voltage) where
voltage (as a pressure) pushes electric
current (as a flow of charge) is
responsible for electric shock.
3.1 Physiological effect of electricity

16. video

17. 30 mA is enough for respiratory
paralysis while 75-100 mA will cause
ventricular fibrillation (rapid &
ineffective heartbeat).
Anything higher than 300mA is fatal
and kills in seconds. 4.5 to 10A will
instantly lead to cardiac arrest, severe
burns and finally death.
The hazardous of electrical shock are the
following:
3.2 Risks
• Loose of motion control
• paralyze
• Respiratory arrest
• Pain
• Physical fatigue
• Ventricular fibrillation
• Cardiac arrest
• Burns
Loose of motion control can cause
pain and secondary injuries due to
falls.

18. Risks of wet
conditions
The average resistance of a human body in dry
condition is almost ≈ 100,000Ω while the
resistance of a human body in wet condition is
1000Ω.
Also, the voltage above 50V (in dry condition)
and 25V (in wet condition) is enough to shock
a person.
Electricity and water make a dangerous
combination, as the water’s ions are extremely
conductive.
3.2
Risks

19. 4.Classes & types • Class (I, II, III) – method of
protection
• Type(B, BF, CF) – degree of
protection
Leakage current
Current that is not functional
which is usually in micro
ampere.
• Earth leakage current
• Enclosure leakage
current
• Patient leakage current
• Patient auxiliary current

20. Leakage
current

21. 5. Codes & Standards
• International electrical
commission (IEC)
• International organization for
standardization (ISO)
• International
telecommunication union
(ITU)
• Institute of electrical and
electronic engineers (IEEE)
• Occupational safety and
health administration (OSHA)
OSHA standards cover many electrical hazards in
many different industries. OSHA's general industry
electrical safety standards are published in:
• 1910.302 through 1910.308 — Design Safety
Standards for Electrical Systems, and
• 1910.331 through 1910.335— Electrical Safety-
Related Work Practices Standards.
OSHA also has electrical safety standards for:
• Construction - in 29 CFR 1926, Subpart K.
• Marine terminals - in 29 CFR 1917, 29 CFR
1917, and longshoring, in 29 CFR
1918 reference the general industry electrical
standards in Subpart S of Part 1910.
• Shipyard standards - 29 CFR 1915, cover limited
electrical safety work practices in 29 CFR
1915.181.

22. Electrical
Safety
Analyzer
Test Measured value IEC 601-1 standard
Protective earth resistance 0.210 ohm 0.200 ohm
Earth leakage current
Nor pol (190 µA)
No l2 (188 µA)
Rev pol (4 µA)
No l2 (40 µA)
500 µA
1000 µA
500 µA
1000 µA
Enclosure leakage current
Nor pol (0 µA)
No l2 (0 µA)
No earth (190 µA)
Rev pol (0 µA)
No l2 (0 µA)
No earth (1µA)
100 µA
500 µA
500 µA
100 µA
500 µA
500 µA
Patient leakage current
Nor pol (2 µA)
No l2 (2 µA)
No earth (21 µA)
Rev pol (0 µA)
No l2 (0 µA)
No earth (1µA)
10 µA
50 µA
50 µA
10 µA
50 µA
50 µA

23. Test Measured value IEC 601-1 standard
Patient auxiliary current
Normal pol, earth, l2
RA-A (0 µA)
RL-A (0 µA)
LA-A (0 µA)
10 µA
10 µA
10 µA
Patient auxiliary current
Normal pol, earth, no l2
RA-A (0 µA)
RL-A (0 µA)
LA-A (0 µA)
50 µA
50 µA
50 µA
Patient auxiliary current
Normal pol, no earth, l2
RA-A (1 µA)
RL-A (1 µA)
LA-A (4 µA)
RA-A (1 µA)
RL-A (1 µA)
LA-A (4 µA)
Electrical
Safety
Analyzer

24. video

25. 6.First Aid &
Precaution
Caution
• Don't touch an injured person who
is still in contact with an electrical
current.
• Call your local emergency number if
the source of the burn is a high-
voltage wire or lightning. Don't get
near high-voltage wires until the
power is turned off. Overhead
power lines usually aren't insulated.
Stay at least 20 feet (about 6
meters) away — farther if wires are
jumping and sparking.
• Don't move a person with an
electrical injury unless there is
immediate danger

26. 6.First Aid & Precaution
Take these actions immediately while waiting for
medical help:
• Turn off the source of electricity, if possible. If not,
use a dry, non-conducting object made of
cardboard, plastic or wood to move the source
away from you and the injured person.
• Begin CPR if the person shows no signs of
circulation, such as breathing, coughing or
movement.
• Try to prevent the injured person from becoming
chilled.
• Apply a bandage. Cover any burned areas with a
sterile gauze bandage, if available, or a clean
cloth. Don't use a blanket or towel, because loose
fibers can stick to the burns.

27. video

28. ● Electrocutions & Shock Injuries: the Basics of Human Electrical
Exposures | Robson Forensic
● Electrical Shock Hazards & Its Effects on Human Body
(electricaltechnology.org)
● Is Voltage or Amperage (Current) More Dangerous?
(oneprojectcloser.com)
● Focus Four - What is an electrocution hazard? - OSHAcademy free
online training (oshatrain.org)
● Electrical shock: First aid - Mayo Clinic
Resources