Industrial Health & Safety

1. 1
Industrial Health & Safety
Accident Prevention
and
Theories of Accident Causation

2. 2
Accident Prevention
 Industrial Place Accidents - Typical Year
Work related accidents cost $48 Billion
7,100,000 injured workers per year
On average, 3 injured workers per 100 workers
One accidental death every 51 minutes
One serious injury every 19 seconds
 To prevent accidents, need to know
why accidents happen and what causes them.
 Accident Causation Theories are used as
models to help predict and prevent accidents.

3. 3
Theories of Accident
Causation
 Domino Theory
 Human Factors Theory
 Accident / Incident Theory
 Epidemiological Theory
 Systems Theory
 Combination Theory

4. 4
Domino Theory
 Herbert Heinrich - Travelers Insurance - 1920’s
 Two Central Points
 Injuries are caused by the actions of preceding
factors.
 Removal of the central factor (unsafe act or
hazardous condition) negates the action of the
proceeding factors; and in doing so, prevents
accidents and injuries.

5. Heinrich’s Axioms of Industrial Safety
 1. Injuries result from a series of preceding factors.
 2. Accidents occur as the result of physical hazard
or an unsafe act.
 3. Most accidents are the result of unsafe behavior.
 4. Unsafe acts and hazards do not always result in
immediate accidents and injuries.
 5. Understanding why people commit unsafe acts
helps to establish guidelines for corrective actions.
5

6. Heinrich’s Axioms of Industrial Safety
6
 6. The severity of the injury is largely fortuitous
and the accident that caused it is preventable.
 7. Best accident prevention techniques are
analogous to best quality / productivity techniques.
 8. Management should assume safety
responsibilities.
 9. The supervisor is the key person in the
prevention of industrial accidents.
 10. Cost of accidents include both direct costs and
indirect costs.

7. 7
Human Factors Theory
 Attributes accidents to a chain of events that were
ultimately the result of human error.
 Three broad factors leading to human error
 Overload
 Inappropriate Responses
 Inappropriate Activities

8. 8
Overload
 Worker’s Capacity -
 Natural Ability, Training, State of Mind,
 Fatigue, Stress, Physical Condition
 Environmental Factors -
 Noise, Climatic, Lighting, Distractions, etc
 Internal Factors -
 Personal Problems, Emotional Stress, Worry
 Situational Factors -
 Level of Risk, Unclear Instructions, Novelty, etc

9. 9
Inappropriate Responses
 Ignores a suspected hazard
 Disregards established safety procedures
 Circumvents safety devices
 Includes incompatibility with person’s workstation
Size, Required Force, Reach, Feel, etc

10. 10
Inappropriate Activities
 Performing tasks without requisite training
 Misjudging the degree of risk

11. 11
Accident/Incident Theory
 Petersen’s Extension to the Human Factors Theory

Adds new elements -
 Ergonomic Traps
 Decision to Err
 System Failures

12. 12
Petersen’s
O v e r l o a d
A c c i d e n t / I n c id e n t T h e o r y
E r g o n o m i c T r a p s D e c s io n t o E r r
H u m a n E r r o r
S y s t e m F a il u r e
A c c id e n t
I n ju r y / D a m a g e

13. 13
Overload
 Pressures
 Deadlines, Budget Factors, Peer Pressure
 Fatigue
 Motivation
 Drugs
 Alcohol
 Worry

14. 14
Ergonomic Traps
 Incompatible Workstation
 Incompatible Expectations

15. 15
Decision to Err
 Misjudgment of Risks
 Unconscious Desire to Err
 Logical Decision Based on Situation /
Circumstances
 Superman Syndrome (It won’t happen to me!)
 - Bulletproof, Invincible, Immortal, Lucky

16. 16
System Failures
 Potential for causal relationship between
managerial decisions/behaviors regarding safety
 Policies
 Responsibilities
 Training
 Inspections
 Corrective Actions
 Standards

17. 17
Epidemiological Theory
 Traditional approaches focused on
 accidents and resulting injuries.
 Current trend includes a broader perspective of
 industrial hygiene issues.
 Industrial Hygiene concerns environmental issues
that can lead to sickness, disease, impaired health.

18. 18
Epidemiological Models
 Used to study causal relationships between
environmental factors and disease.
 Theory supposes these models are also
appropriate for studying the casual relationships
between environmental factors and accidents.
 Note: Causal NOT Correlational Relationships !!!

19. 19
Epidemiological Theory
E p id e m io lo g ic a l T h e o r y
P r e d is p o s it io n a l
C h a r a c t e r is t ic s
S it u a t io n a l
C h a r a c t e r is t ic s
C a n c a u s e o r p r e v e n t a c c id e n t c o n d it io n s

20. Systems Theory of Causation
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 System is a group of interacting and interrelated
components that form a unified whole.
 Host (People) Agent (Machinery) Environment
 The likelihood of an accident occurring is
determined by how these components interact.
 Changes in the patterns of interaction can increase
or decrease the probability of an accident occurring.

21. 21
Firenzie’s Systems Theory
 Person/Machine/Environment
 Information Gathering
 Risks Assessment
 Decision Making
 Task Performance
Stressors
 Stressors can cloud the judgment during
information gathering, risk weighing, decision
making processes.

22. Firenzie’s Recommendations
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 Consider Five Factors -
before beginning the process of information
gathering, risk weighing, decision making.
 Job Requirements
 Worker’s Abilities and Limitations
 Gain from Successful Task Completion
 Loss if Task Attempted but Results in Failure
 Loss if Task is Not Attempted

23. Combination Theory of Causation
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 Theories and models are not necessarily reality.
 A single theory may not suit all circumstances.
 Some theories address particular problems better
than other theories.
 A combination of theories and models may be the
optimal approach toward problem solutions.