Hazards Definition
• Hazard is the potential of a substance to cause
damage.
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Classification & Potential Sources of Hazards
Classification Example of Hazards
• Mechanical - Sharp points & edges, overload.
• Electrical - Insulation damaged or cover broken
• Biological - Exposed, airborne/blood borne
• microorganism.
• Chemical - Expose to carcinogens chemical
• Ergonomics - Expose to unnatural postures
• Psychological - Stress or violent at workplace.
Hazards: Different types of energies in
workplace
Potential
Energy
Kinetic
Energy
Thermal Electrical
Chemical
Energy Energy
Energy
Chemical Hazards
New workers working with paints might be exposed to paint
thinners and solvents that they could breathe in or get on their
hands.
Workers who work as cleaners will likely be exposed to cleaning
solvent solutions like ammonia, which can be harmful if it is
inhaled or gets on the skin, or if it is mixed with other chemicals
Hazardous chemicals can enter the body in several ways: they can
be breathed in (inhalation), they can be swallowed (ingestion)
and they can be absorbed through the skin (absorption).
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2007 Most Toxic Hazardous
Substances List (ATSDR)
2007 2005
SUBSTANCE NAME
Rank RANK
1 ARSENIC 1
2 LEAD 2
3 MERCURY 3
4 VINYL CHLORIDE 4
5 POLYCHLORINATED BIPHENYLS 5
6 BENZENE 6
7 CADMIUM 8
POLYCYCLIC AROMATIC
8 7
HYDROCARBONS
9 BENZO(A)PYRENE 9
10 BENZO(B)FLUORANTHENE 10
Chemical Hazard Identification
Physical / Mechanical Hazards
• Physical hazards include things like equipment, machinery etc.
noise, heat and cold.
Machinery can range from heavy machinery, like a press or a
stamping machine, to smaller equipment such as meat slicers or
paper cutters.
Excessive noise levels or prolonged noise can damage the nerves
in the ear causing temporary or even permanent hearing loss
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Physical Hazards: Can you find the hazard(s)?
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unguarded
saw blade
2 Unguarded chain
and Sprocket
1 Unguarded belt and pulley
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Physical Hazards: Can you find the hazard(s)?
Hands are too close to
machine
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Physical Hazards: How about now
Hands are too close to
machine
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Biological Hazards
• Workers who are most at risk from biological hazards are those
who work with animals or plants, or in healthcare. and cold.
Biological agents are living substances that can cause illness or
disease. They include bacteria, viruses and fungi. Bacterial are
found in the air, water and soil and in living or dead animals or
plants.
Viruses, bacteria and fungi can be passed from one person to
another, either directly through contact with body fluids, or
indirectly through breathing.
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Ergonomic Hazards
Ergonomics means adapting the workplace to the worker, instead of
trying to adapt the worker to the workplace. If the work station,
tools and equipment, physical environment including lighting,
temperature and noise are not properly designed, undue stresses
and strains can be placed on the musculoskeletal system.
Injuries that cause disorders of the muscles, bones, blood vessels,
tendons, nerves and other soft tissues in the body may develop in
workers who:
• Maintain fixed positions.
• Perform repetitive movement of the limbs.
• Work with great speed along with repetitions.
Ergonomic Hazards
Hazard Identification Techniques
Identifying hazard means:
1.The hazardous characteristic
2. The form and quantity of the hazard
3. Where and when in the system it is present
4. Under what conditions could the hazard propagate into an
undesirable event (i.e., accident)
Methods:
Checklists - questions to assist in hazard identification
What If Analysis - possible outcomes of change
HAZOP - identifies “process plant” type incidents
Fault Tree Analysis - combinations of failures
FMEA/FMECA - equipment failure causes
Checklists
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What if Analysis
• “What–If” Hazard Analysis is a structured brainstorming method of
determining what things can go wrong and judging the likelihood and
severity of those situations occurring.
• Analyzer uses questions posed in the form of “What if...?” statements,
such as; “What if the cooling water to the chamber stops?”
• The team then continues to determine what the outcome would be
(assuming there were no protections).
• Chamber overheating, element burn out, bad process etc.
• From here the team then determines if systems and protections are in
place to protect against these occurrences.
• Cooling water flow switch that shuts down process when it gets below XX
set point,” or “Over temperature interlock switch on the chamber that
shuts down power to the chamber heat source when the temperature
reaches XX°C.”
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What if Analysis
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Hazard and Operability Analysis
A Hazard and Operability (HAZOP) study is a structured and systematic
examination of a planned or existing process or operation in order to
identify and evaluate problems that may represent risks to personnel or
equipment, or prevent efficient operation.
The HAZOP technique was initially developed to analyze chemical
process systems, but has later been extended to other types of systems
and also to complex operations and to software systems.
A HAZOP is a qualitative technique based on guide-words and is carried
out by a multi-disciplinary team (HAZOP team) during a set of meetings.
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HAZOP Guide Words
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Guide Words associated with problems
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Example
The process: delivery of liquid propane to a fixed tank currently fitted with a
pressure relief valve
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Fault Tree Analysis
• Graphical model that displays the various
combinations of equipment failures and
human errors that can result in the main
system failure of interest.
• Identification/assessment of risk is derived by
first identifying faults/hazards.
• A top down approach.
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Definitions
• FAULT
An abnormal undesirable state of a system or a system element
induced 1) by presence of an improper command or absence of a
proper one, or 2) by a failure (see below). All failures cause faults;
not all faults are caused by failures. A system which has been shut
down by safety features has not faulted.
• FAILURE
Loss, by a system or system element*, of functional integrity to
perform as intended, e.g., relay contacts corrode and will not pass
rated current closed, or the relay coil has burned out and will not
close the contacts when commanded –the relay has failed; a
pressure vessel bursts –the vessel fails.
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Fault Tree Analysis
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Construction of Fault Tree
• Each node in the tree can be represented by a
combination of events that cause the
occurrence of the event, by means of logic
gates
• Each gate has inputs and outputs
• An input can be a basic event or an output of
another gate
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Construction of Fault Tree
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Fault Tree Symbols
Primary Event Symbols Gate Symbols
AND
Basic Event
OR
Conditioning Event
Exclusive OR
Undeveloped Event
Priority AND
External Event Inhibit
Intermediate Event Symbol Transfer Symbols
Transfer IN Transfer OUT
Fault Tree Symbols
Primary Event Symbols
Basic Event
Conditioning Event
Undeveloped Event
External Event
Fault Tree Symbols
Gate Symbols
AND
OR
Exclusive OR
Priority AND
Inhibit
Fault Tree Symbols
Intermediate Event Symbol
Transfer Symbols
Transfer IN Transfer OUT
Union
No Current A=B + C
A
A=B Union C
B OR C must occur
for event A to occur
B C
Switch A Battery B
Open 0 Volts
Intersection
Over-heated D=E * F
D Wire
D= E Intersection F
E AND F must occur
for D to occur
E F
5mA Current Power Applied
in System t >1ms
Another Example
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