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This material is for training purposes only. Its purpose is to inform employers and employees of best practices in occupational safety and health and general OSHA compliance requirements. This material is not a substitute for any provision of the Occupational Safety and Health Act or any standards issued by OSHA.
 MODULE FIVE: DETERMINE SURFACE AND ROOT CAUSES
Introduction
We've gathered information and used it to develop an accurate sequence of events. We've got a good mental picture of what happened. Now it's time to conduct an analysis of each event to determine causes. This module will introduce us to the following concepts:
- Injury analysis
- Event analysis
- Systems analysis
- Direct cause of injury
- Surface cause of the accident
- Root cause of the accident
Actors and Actions
In the last module we learned that each event in our sequence will include descriptions of actors and their actions that may have contributed to the accident.
Our next step is to examine each event to determine:
- the actor that represents a hazardous condition, and
- action that represents an unsafe behavior.
The hazardous conditions and unsafe behaviors we identify as contributing to the accident are called the surface causes of the accident.
After we identify surface causes, we'll need to determine if inadequate safety system components contributed to the accident by allowing the hazardous conditions and unsafe behaviors to develop or occur. These system inadequacies are called the root causes of accidents. Let's take a closer look at these two very important concepts.
The surface causes of accidents
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The surfaces causes of accidents are those hazardous conditions and unsafe employee/manager behaviors that have directly caused or contributed in some way to the accident.
Hazardous conditions:
- are basically things or objects that cause injury or illness
- may also be thought to be defects in a process
- may exist at any level of the organization
Hazardous conditions may exist in any of the following categories:
- Materials
- Machinery
- Equipment
- Tools
- Chemicals
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- Environment
- Workstations
- Facilities
- People
- Workload
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It's important to know that most hazardous conditions in the workplace are the result of an unsafe behaviors that produced them.
Unsafe behaviors:
- are actions we take or don't take that increase risk of injury or illness.
- may also be thought to be errors in a process
- may occur at any level of the organization.
Some example of unsafe employee/manager behaviors include:
- Failing to comply with rules
- Using unsafe methods
- Taking shortcuts
- Horseplay
- Failing to report injuries
- Failing to report hazards
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- Allowing unsafe behaviors
- Failing to train
- Failing to supervise
- Failing to correct
- Scheduling too much work
- Ignoring worker stress
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The direct cause of injury is not the cause of the accident
If we examine the surface cause categories above, we find that each may somehow produce a harmful level of energy> that may be transferred to our body directly causing an injury. Here are the various forms of energy that can be harmful:
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Harmful forms of energy may include:
1. ACOUSTIC ENERGY - Excessive noise and vibration.
2. CHEMICAL ENERGY - Corrosive, toxic, flammable, or reactive substances. Involves a release of energy ranging from "not violent" to "explosive" and "capable of detonation".
3. ELECTRICAL ENERGY - Low voltage (below 440 volts) and high voltage (above 440 volts).
4. KINETIC (IMPACT) ENERGY - Energy from "things in motion" and "impact," and are associated with the collision of objects in relative motion to each other. Includes impact between moving objects, moving object against a stationary object, falling objects, flying objects, and flying particles. Also involves movement resulting from hazards of high pressure pneumatic, hydraulic systems.
5. MECHANICAL ENERGY - Cut, crush, bend, shear, pinch, wrap, pull, and puncture. Such hazards are associated with components that move in circular, transverse (single direction), or reciprocating motion.
6. POTENTIAL (STORED) ENERGY - Involves "stored energy." Includes objects that are under pressure, tension, or compression; or objects that attract or repulse one another. Susceptible to sudden unexpected movement. Includes gravity - potential falling objects, potential falls of persons. Includes forces transferred biomechanically to the human body during lifting.
7. RADIANT ENERGY HAZARDS - Relatively short wavelength energy forms within the electromagnetic spectrum. Includes infra-red, visible, microwave, ultra-violet, x-ray, and ionizing radiation.
8. THERMAL ENERGY - Excessive heat, extreme cold, sources of flame ignition, flame propagation, and heat related explosions.
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The harmful transfer of energy is the direct cause of injury. Let's take a look at three examples:
- If a harsh acid splashes on our face, we may suffer a chemical burn because our skin has been exposed to a chemical form of energy that destroys tissue. In this instance, the direct cause of the injury is a harmful chemical reaction. The related surface cause might be the acid (condition) or working without proper face protection (unsafe behavior).
- If our workload is to too strenuous, force requirements on our body may cause a muscle strain. Here, the direct cause of injury is a harmful level of kinetic energy (energy resulting from motion), causing injury muscle tissue. A related surface cause of the accident might be fatigue (hazardous condition) or improper lifting techniques (unsafe behavior).
The important point to remember here is that the "direct cause of injury" is not the same as the surface cause of the accident. To summarize:
- The surface cause of the accident describes a condition or behavior. The result of the condition and/or behavior is the direct cause of injury...a harmful transfer of energy.
- The direct cause of injury is the harmful transfer of energy. The direct result is injury.
Safety "engineers" closely analyze all the surface cause categories and attempt to:
- eliminate the harmful energy,
- reduce the harmful energy transfer, or
- reduce exposure to harmful energy transfer.
They do this by designing safety features directly into tools, machinery, equipment, facilities, etc.
The root causes of accidents
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The root causes for accidents are the underlying safety system weaknesses that have somehow contributed to the existence of hazardous conditions and unsafe behaviors that represent surfaces causes of accidents. These weaknesses can take two forms:
- System Design Root Causes. Inadequate design of one or more components of the safety management system. The design of safety management system policies, plans, programs, processes, procedures and practices (remember this as the 6-P's) is very important to make sure appropriate conditions, activities, behaviors, and practices occur throughout the workplace. Ultimately, most surface causes will lead to system design flaws.
- System Implementation Root Causes. Inadequate implementation of one or more components of the safety management system. Failure to effectively implement the safety management system is critical to the success of the system. You may design an effective safety plan, yet suffer failure because it wasn't implemented properly. If you effectively implement a poorly written safety plan, you'll get the same results. In either instance, you'll eventually need to improve one or more policies, plans, programs, processes, procedures or practices.
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Safety managers work with safety engineers to eliminate or reduce exposure to hazards through effectively improving safety system components. Because systems design work common throughout the workplace, eliminating any single root cause may simultaneously eliminate many hazardous conditions and unsafe behaviors.
Since root causes reside within safety management systems, upper management -- those who formulate systems, are most likely going to be involved in making the necessary improvements. When analyzing for system weaknesses, it may be beneficial to coordinate closely with those who will be responsible for implementing system improvements.
If you have Adobe Acrobat, take a look at the Accident Weed, an excellent analogy that helps us understand the relationship between surface and root causes for accidents.
Three levels of cause analysis
As mentioned earlier in the course, accidents are processes that culminate in an injury or illness. An accident may be the result of many factors (simultaneous, interconnected, cross-linked events) that have interacted in some dynamic way. In an effective accident investigation, the investigator will conduct three levels of cause analysis:
Injury analysis. At this level of analysis, we do not attempt to determine what caused the accident, but rather we focus on trying to determine how harmful energy transfer caused the injury. Remember, the outcome of the accident process is an injury.
Event Analysis. Here we determine the surface cause(s) for the accident: Those hazardous conditions and unsafe behaviors described throughout all events that dynamically interact to produce the injury. All hazardous conditions and unsafe behaviors are clues pointing to possible system weaknesses. This level of investigation is also called "special cause" analysis because the analyst can point to a specific thing or behavior.
Systems analysis. At this level we're analyzing the root causes contributing to the accident. We can usually trace surface causes to inadequate safety policies, programs, plans, processes, or procedures. Root causes always pre-exist surface causes and may function through poor component design to allow, promote, encourage, or even require systems that result in hazardous conditions and unsafe behaviors. This level of investigation is also called "common cause" analysis because we point to a system component that may contribute to common conditions and behaviors throughout the company.
| The biggest challenge to effective accident investigation is to transition from event analysis to systems analysis. |
One last important point to make is that most accident processes are far more complex than we might originally think. Some experts believe at least 10 or more factors come together to cause a serious injury. Other experts state that, on average, 27 factors directly and indirectly contribute to serious accidents.
Only by thoroughly conducting all three levels of analysis can we design system improvements that effectively eliminate hazardous conditions and unsafe behaviors at all levels of the organization. The accident investigation can not serve as a proactive safety process unless system improvements effectively prevent future accidents.
Event Analysis
Well, we know that surface and root causes are, and we know all about the three levels of analysis required for an effective investigation, but what techniques can we use to do help us do the analysis? Let's take a look at one technique that I have found efficient in conducting an event analysis.
I've modified the commonly used "fishbone diagram," used successfully by many as a general problem solving tool, to help conduct an event analysis.
- Get a sheet of paper.
- At the top of the sheet write "Accident Analysis". Doing this reminds you that you are breaking down the process into a number of events.
- At the left side of the sheet, centered, write "The Injury".
- Extend a horizontal line out from the right of the box.
- Describe the injury event on the horizontal line.
- Identify and circle the actors and actions described in the event statement.
- Start asking why questions about the actor and actions to uncover any hazardous conditions or unsafe behaviors.
- Draw lines either angling up or down from the circled actors and actions and write the answers to your questions.
- Repeat these steps with each of the new level of answers.
The diagram you produce using this procedure should look something like this. Each level of questioning will get you closer to the root cause(s) that allowed the hazardous condition or unsafe behavior. Once you start identifying inadequate policies, programs, plans, processes, and procedures...you are getting to the real root causes!
Finally, it's important to understand that most accidents in the workplace result
from unsafe work behaviors. According to the latest research, they represent the direct cause for about 95% of all workplace accidents. Hazardous conditions represent the direct cause for only about 3% of workplace accidents. "Acts of God" account for the remaining 2%. All these statistics imply that management system weaknesses account for fully 98% of all workplace accidents. To effectively fulfill our responsibilities as an accident investigator, we must not close the investigation until these root causes have been identified.
Whew! Another great module...only task left is to complete the quiz, so let's go.
Take the Review Quiz
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