Using a causation model when investigating HAZCHEM incidents

Apr 3, 2019 Posted by Walter Ingles

The primary reason for investigating any workplace incident is to understand why the incident happened and then introduce measures to prevent it from happening again. To get a better understanding of the causes of an incident, many WHS professionals use causation models during the investigation process. This blog takes a quick look at the evolution of causation models and offers a simple framework to apply to your next incident investigation (particularly if hazardous chemicals were involved.)

Types of causation models

Since the early 1930s Occupational Safety Professionals have developed causation models to gain greater insight into the factors that contribute to dangerous incidents. They have evolved through these three stages.

1. Simple linear models

The earliest incident causation models assumed that a series of events occur in a linear sequence, and this sequence is the ultimate cause of the incident. In this model each step in the sequence is dependent on the other (a bit like dominos falling) — so if you could eliminate any fault within the sequence, the incident could have be prevented. For example:

  1. Worker is moving a gas bottle on a trolley

  2. There is no safety strap in place

  3. Gas bottle falls off the trolley

  4. Gas bottle explodes

  5. Worker is killed

From the example above, a simple linear model would assume that fixing the strap on the gas bottle trolley would prevent further incidents.

2. Complex linear models 

These models attribute the cause of an incident to a more complex series of events. There is still a linear sequence in place but multiple events are included in the sequence. For example:

  1. Worker is moving a gas bottle on a trolley

  2. There is no safety strap in place

  3. [Worker distracted by nearby forklifts] Gas bottle falls off the trolley [trolley wheel jams]

  4. Gas bottle explodes

  5. Worker is killed

Referring again to our example, the complex linear model acknowledges that other factors contributed to the incident, but still focuses on resolving the problem by removing faults from the sequence — ie, getting the trolley fixed.

3. Complex non-linear models

Most causation models used today recognise that dangerous incidents are the result of a combination of factors (sometimes seemingly unrelated). For example:

  1. [there is no system of equipment inspections, routine maintenance, and pre-operational checks]
  2. Worker is moving a gas bottle on a trolley
  3. There is no safety strap in place [same worker has been using a trolley which hasn’t had a strap for more than a month]
  4. [Worker distracted by nearby forklifts] Gas bottle falls off the trolley [debris on floor] [trolley wheel jams]
  5. Gas bottle explodes
  6. Worker is killed

In the example above, the complex non-linear model looks at a whole range of factors that contributed to the incident. In the next section we look at a simple model which assigns causal factors into logical groups.

 

Simple causation model: assigning factors into groups

Here at STOREMASTA we suggest using a simple model which assigns individual causation factors into five distinct groups: TASK, MATERIAL, ENVIRONMENT, PERSONNEL, MANAGEMENT.  Let’s look more closely at each of the five groups:

  1. TASK (examine the work procedures that were being carried out the time of the incident)

    Questions to ask. Had a safe work method been issued and was it being followed? Was the work procedure suited to the task and equipment?

  2. MATERIAL (examine the machinery, tools, equipment, and substances being used)

    Questions to ask. Were chemicals being used and stored according to Safety Data Sheets? Did a chemical container break? Did a machine malfunction? Did PPE fail? Did an obstruction cause a worker to fall? Were all safety signs in place?

  3. ENVIRONMENT (evaluate the prevailing environmental conditions)

    Questions to ask. Was the weather unseasonably hot or cold? Were there heavy winds? Was production schedule higher than normal? Were hazardous fumes, dusts, or gases present? Were housekeeping standards poor?

  4. PERSONNEL (evaluate the physical condition and mental state of the worker)

    Questions to ask. Were any workers affected by prescription medication? Was the worker stressed or fatigued? Did a worker faint or have an allergic reaction?

  5. MANAGEMENT (evaluate the impact of management)

    Questions to ask. Were safety audits and inspections regularly conducted? Were hazard control measures in place? Were workers being supervised? Had workers been trained to understand chemical hazards? Were safe working procedures enforced?

Simple causation model in practice

During a real investigation you systematically consider possible causes from each group. To demonstrate we’ll use the same example of the worker and the gas bottle.

  1. Task - the gas cylinder was strapped in by the worker using the trolley. The worker did not check the integrity of the strap before moving the trolley. There was no procedure in place for this to happen.

  2. Material - the cylinder trolley had no safety strap. The trolley had not been inspected for several months. On closer inspection a buildup of debris had caused the wheel to jam.

  3. Environment - there were a lot of forklifts operating in the area and the worker had to stop several times to let them pass. Housekeeping was at a low standard and a lot of refuse and debris was lying around.

  4. Personnel - the worker had just returned from sick leave and was not at their usual level of fitness. They were observed to be sweating and breathing heavily as they moved the cylinder.

  5. Management - there was no established procedure for pre-operational equipment inspections. Supervisors were not enforcing housekeeping policies. 

Causation models are a useful tool when carrying out an investigation and there are many established causation models if you are interested in creating your own incident investigation methodology.

 

Any questions, comments or queries? Feel free to contact one of our friendly team here.  Alternatively, you can call us on our support line: 1300 134 223

Walter Ingles

Walter Ingles Compliance Specialist

Walter is STOREMASTA’s Dangerous Goods Adviser. He loves helping businesses reduce the risk that Dangerous Goods pose upon their employees, property and the environment through safe and compliant dangerous goods storage solutions.

Like what you’re reading?

Subscribe to stay up tp date with the latest from STOREMASTA®


Recommended Resources

Dangerous Goods Segregation Guide
A PRACTICAL EBOOK

How to segregate incompatible classes of dangerous goods

Segregate the 9 different classes of dangerous goods in a way which will reduce risk to people, property, and the environment.

Learn more

Preserving the scene after an incident involving hazardous chemicals
From the blog

Preserving the scene after an incident involving hazardous chemicals

After an incident involving hazardous chemicals — apart from the distressing task of attending to injured or deceased ...

Learn more

Using a causation model when investigating HAZCHEM incidents
From the blog

Using a causation model when investigating HAZCHEM incidents

The primary reason for investigating any workplace incident is to understand why the incident happened and then ...

Learn more

HAZCHEM Alert: understanding workplace accidents, incidents and dangerous events
From the blog

HAZCHEM Alert: understanding workplace accidents, incidents and dangerous events

This blog is about workplace ‘incidents’  — meaning an event which happens in the workplace and threatens the overall ...

Learn more

4 steps to running an effective HAZCHEM incident investigation
From the blog

4 steps to running an effective HAZCHEM incident investigation

An effective HAZCHEM incident investigation quickly gets to the root causes of a workplace incident and identifies ...

Learn more