What Is the Human Factors Dirty Dozen?
The Human Factors "Dirty Dozen" refers to twelve of the most common human error preconditions — conditions that can act as precursors to accidents or incidents in safety-critical environments. The concept highlights how everyday factors influence people to make mistakes, not through carelessness or bad intentions, but through circumstances that degrade judgment, attention, and performance without those involved necessarily realizing it.
Understanding these preconditions is one of the most practical steps an airport organization can take toward building a stronger safety culture. When people can name the conditions that put them at risk, they are far better equipped to recognize and manage them in real time.
Origins of the Dirty Dozen
The Dirty Dozen concept was developed by Gordon Dupont in 1993 while working for Transport Canada, originally as part of an introductory Human Performance in Maintenance training program. Since then, it has become a cornerstone of human factors education worldwide, widely applied in aircraft maintenance, airport operations, and aviation safety programs across the industry.
The Twelve Preconditions
Each of the following factors can reduce performance and increase the likelihood of errors if not proactively managed:
- Lack of communication
- Distraction
- Lack of resources
- Stress
- Complacency
- Lack of teamwork
- Pressure
- Lack of awareness
- Lack of knowledge
- Fatigue
- Lack of assertiveness
- Norms
These twelve factors are not abstract theoretical risks. They are present in airport operations every day, in shift handovers where communication breaks down, in high-pressure periods where teams cut corners, in experienced staff who become complacent with familiar procedures, and in fatigue that subtly erodes attention and decision-making without the person affected always recognizing it. Detailed explanations of each precondition are available through Skybrary.
The Role of Human Factors Safety Training
Human factors safety training is the primary tool for addressing the error preconditions identified by the Dirty Dozen. Effective training helps organizations recognize risks early, establish clearer defenses, and build a culture where people feel both empowered and responsible for calling out conditions that could lead to error.
Our Human Factors Safety Training Course
The Human Factors Safety Training course supports airports in strengthening their safety culture by improving awareness of the factors that influence human performance. It provides participants with a comprehensive introduction to core human factors concepts, enabling them to recognize, understand, and prevent errors in airside operations.
On completion, participants are equipped to apply practical human factors strategies within their day-to-day roles, making the insights from the Dirty Dozen framework directly actionable rather than purely theoretical.