Barriers, or controls, are one of the (not-at all) secret sauces of root cause analysis.
By understanding barriers we can understand both why a problem happened and how it can be prevented in the future. An evaluation of current process controls as part of root cause analysis can help determine whether all the current barriers pertaining to the problem you are investigating were present and effective (even if they worked or not).
At its simplest it is just a three part brainstorm:
|Barriers that failed||The barrier was in place and operational at the time of the accident, but it failed to prevent the accident.|
|Barriers that were not used||The barrier was available, but workers chose not to use it.|
|Barriers that did not exist||The barrier did not exist at the time of the event. A source of potential corrective and preventive actions (depending on what they are)|
The key to this brainstorming session is to try to find all of the failed, unused, or nonexistent barriers. Do not be concerned if you are not certain which category they belong in.
Most forms of barrier analysis look at two types, technical and administrative. My company breaks the administrative into human and organization, and I have to admit that breakdown has grown on me.
|If||A technical or engineering control exists||The control relies on a human reviewer or operator||The control involves a transfer of responsibility. For example, a document reviewed by both manufacturing and quality.|
|Examples||Separation among manufacturing or packaging lines
Emergency power supply
Keypad controlled doors
Separated storage for components
Software which prevents a workflow going further if a field is not completed
|Training and certifications
Use of checklist
Verification of critical task by a second person
|Clear procedures and policies
Adequate load of work
Periodic process audits
These barriers are the same as current controls is in a risk assessment, which are key in a wide variety of risk assessment tools.