1. How Accidents Happen

2. How Accidents Happen There are no absolute hazard controls.
Every control has holes.

3. How Accidents Happen There are no absolute hazard controls.
Every control has holes.
Some controls have more holes than others.
People make mistakes, so anything that requires human interaction has more holes than fixed controls.
Training, warning signs, and PPE have the most holes.

4. How Accidents Happen There are no absolute hazard controls.
Every control has holes.
Some controls have more holes than others.
People make mistakes, so anything that requires human interaction has more holes than fixed controls.
Training, warning signs, and PPE have the most holes.

5. How Accidents Happen
Each control is a layer of defense. The more layers and the fewer holes, the greater the defense against an accident.
Engineered Controls
HAZARD
Administrative Controls
Contributing Factors
Environmental Factors
Organizational Factors
Behavioral Factors
Accident

6. How Accidents Happen
Each control is a layer of defense. The more layers and the fewer holes, the greater the defense against an accident.
Engineered Controls
HAZARD
Administrative Controls
Contributing Factors
Environmental Factors
Organizational Factors
Behavioral Factors
Accident
An accident occurs when all the defenses are defeated.

7. How Accidents Happen
We poke additional holes in our defenses each time we:
Allow unsafe behavior to occur without taking immediate action
Walk by an uncontrolled hazard without taking action to control it
We completely remove a defense when we circumvent safety policies!

8. How Accidents Happen We improve our workplace safety by:
Implementing the best practical engineered controls (those with the fewest holes)
We add back-up controls (additional defenses)
We add and enforce administrative controls such as policies, safety instructions, and signage
We add and enforce wearing of correct PPE