Fundamental Concepts & Terms

1. Fundamental Concepts & Terms IENG 331 Safety Engineering

2. Why Safety? • Read Chapter 3! • Humanitarian Reasons • Regulatory Reasons • Economic Reasons

3. What is an Accident? • An event that is not expected or intended • Could cause • injury • loss • Implies “chance”

4. Fundamental Accident Causes • Unsafe Acts • Unsafe Conditions • Both • “Not necessarily a ‘chance’ event”

5. Injury illness disease death damage to property, equipment, materials cost of replacement legal & medical services Loss of time, production, sales time to complete forms recordkeeping investigations cleanup hospitalization, rehab public image damage Types of Losses

6. Losses: Direct vs Indirect Costs • Direct (Obvious) • medical expenses, WC, repair or replace damages • Indirect (Not Obvious) • 4:1 Ratio • Iceberg Theory • See Table 3-1

7. Unsafe Acts vs Unsafe Conditions • Heinrich analyzed 75,000 accidents • 88 : 10 : 2 ratio • 88% unsafe acts • 10% unsafe conditions • 2% unpreventable causes • Engineers can attack unsafe conditions • Must understand human behavior and management principles to attack unsafe acts

8. Accident - Injury Relationship • Heinrich’s 300 : 29 : 1 ratio • For 330 accidents • 300 result in no injury • 29 produce minor injuries • 1 produces major, lost-time injury • Opportunities to improve are great • Many accidents are “rehearsed” many times

9. Accident - Costs Relationship • Pareto Relationship • 80% - 20% rule • 80% of the costs are related to 20% of the injuries • for example, low back lifting injuries represent 20% of all accidents, but represent 80% of the costs • if you can manage and control that 20% of accidents, you can control 80% of the costs • Figure 3-1 shows 50% of the costs are related to 2% of the injuries • “the powerful few”

10. Terms • Safety: being relatively free from harm, danger, damage, injury • Risk: measure of both frequency and severity of hazards • Hazard: unsafe condition, the potential for an activity or condition to produce harm • Safety Engineering: application of engineering principles to the recognition and control of hazards

11. Accident Theories • Domino Theory • Energy Theory • Single Factor Theories • Multiple Factor Theories

12. Domino Theory (Heinrich) • Injury is caused by • Accidents which are caused by • Unsafe acts or conditions which are caused by • Undesirable traits (e.g., recklessness, nervousness, temper, lack of knowledge, unsafe practices) which are caused by • Social environment

13. Domino Theory Cont. • Stop the sequence by removing or controlling contributing factors • Strong emphasis is placed on the middle domino: unsafe acts or conditions

14. Energy Theory (Haddon) • Accidents & Injuries involve the transfer of energy, e.g., fires, vehicle accidents, projectiles, etc. • Transfer of energy from a “potential” to “kinetic” • Attack problems in parallel rather than serial (as is presumed in Domino Theory)

15. Energy Theory Cont.10 Strategies to Prevent or Reduce 1. Prevent the marshalling of energy. - don’t produce the energy - don’t let kids climb above floor level - don’t produce gun powder 2. Reduce the amount of energy marshalled. - keep vehicle speeds down - reduce chemical concentrations - don’t let kids climb above 3’

16. 3. Prevent the release of energy - elevator brakes 4. Modify the rate at which energy is released from its source or modify the spatial distribution of the released energy. - reduce the slope on roadways 5. Separate in space or time the energy being released from the structure that can be damaged or the human who can be injured. - separate pedestrians from vehicles

17. 6. Separate the energy being released from a structure or person that can suffer loss by interposing a barrier. - safety glasses, highway median barriers 7. Modify the surfaces of structures that come into contact with people or other structure. - rounded corners, larger surface areas for tool handles 8. Strengthen the structure or person susceptible to damage. -fire or earthquake resistant structures, training, vaccinations

18. 9. Detect damage quickly and counter its continuation or extension. - sprinklers that detect heat - tire tread wear bands 10. During the period following damage and return to normal conditions, take measures to restore a stable condition. - rehab an injured worker - repair a damaged vehicle

19. Single Factor Theories • Assumes that when one finds a cause, there is nothing more to find out. • Weak theory, there can be so much more to learn!

20. Multiple Factor Theories • Accidents are caused by many factors working together • The theory and the analysis is more complex, but more realistic than Single Factor Theory • Consider the Four M’s: • management, man, media, machine • And their interactions

21. Preventative Strategies • Proactive vs. Reactive • Frequency strategies • Severity strategies • Cost strategies • Combinations • Three E’s of Safety: engineering, education, enforcement

22. How Safe is Safe Enough? • Can absolute safety be achieved? • Remember the concept of “risk”. • What is “acceptably safe”?

23. HW3 – Chapter Three • Review Questions (p. 24-25) • 2, 5, 8, 11, 14, 17, 20 • 15 points • Due 9/15 (beginning of class)