Occupational risk management
In the matrix, dielectric gloves lower the electric shock risk at the bench from 15 to 10. An isolation transformer with a residual-current device lowers it to 4: it pays to act on the hazard.
01Hazard and risk
A hazard is a source of possible harm: a 220 V voltage, a flammable solvent, a ladder. Risk combines the likelihood that the harm occurs with the severity of its consequences. The same hazard can give very different risks: 220 V in a closed panel with an RCD is not the same as 220 V in an open power supply on the bench.
02Identifying hazards
What has not been identified cannot be managed. The techniques range from the simplest to the most systematic:
| Technique | How it works | When to use it |
|---|---|---|
| Checklists | Predefined questions by type of hazard | Routine inspections |
| Job safety analysis | Steps of the task with their hazards | Manual and maintenance tasks |
| What if...? | A group proposes deviations and analyzes their effects | New processes, changes |
| HAZOP | Guide words (more, less, no, reverse) applied to each process variable | Continuous process plants |
| FMEA | Failure modes of each component, their effects and their detection | Design of equipment and products |
The participation of workers is part of the method: the person who does the task knows deviations and shortcuts that do not appear in any drawing.
03Evaluating: the risk matrix
Each hazard is placed in a likelihood-by-consequence matrix, and the product is classified into levels that indicate what to do. A common classification for scales from 1 to 5:
| Value of R | Level | Action |
|---|---|---|
| 1 to 4 | Low | Maintain the existing controls |
| 5 to 9 | Moderate | Reduce when reasonable; plan |
| 10 to 16 | High | Reduce as a priority before continuing, or with immediate measures |
| 20 and 25 | Intolerable | Do not start or continue the work until it has been reduced |
The underlying criterion is the ALARP principle (as low as reasonably practicable): a risk is reduced as long as the cost of reducing it is not disproportionate to the benefit. Measures are chosen using the hierarchy of controls, and the risk that remains after applying them, the residual risk, is evaluated again.
Four hazards of a laboratory, with their estimated likelihood and consequence. For each one you choose the control; the hollow dot is the initial risk and the filled one the residual risk. The estimates are a reasoned example, not table values.
04A management system
Evaluating once is not enough: processes, people and equipment change. A management system turns prevention into a cycle of continual improvement: plan, do, check and act. The ISO 45001 standard organizes it with the common structure of ISO management standards:
- Context and leadership: management takes responsibility, and workers participate and are consulted.
- Planning: hazard identification, risk assessment, legal requirements and objectives.
- Support and operation: resources, competence, communication, operational controls and emergency preparedness.
- Evaluation and improvement: monitoring, internal audits, management review, incident investigation and corrective actions.
The legal requirements of the legal framework enter the system as one more requirement: the standard does not replace them.
05In the laboratory
Identify the hazards of the university laboratory with a checklist, estimate them in the matrix and propose controls for those that remain at a high level.
In a group, apply the technique to the charging of lithium batteries in the laboratory: what happens if one is short-circuited, if it is overcharged, if it is punctured, if no one is present.
Do a simplified FMEA of a bench power supply, from the point of view of the safety of the person who uses it.
06Common mistakes
- Confusing hazard with risk. The hazard is the source; the risk is how likely and how serious its harm is.
- Believing that the matrix gives an exact number. It orders and prioritizes; its values are estimates.
- Lowering the risk with PPE alone. It reduces the likelihood a little and does nothing to the potential severity of the hazard.
- Evaluating once and filing it away. Every change of process, equipment or staff requires evaluating again.
07Self-assessment
A hazard has likelihood 3 and consequence 4. At what level does it fall?
R = 12: high.
What does ALARP mean?
Reducing the risk as far as is reasonably practicable, until the cost is disproportionate to the benefit.
Which technique would you use to analyze the hazards of a continuous chemical plant?
HAZOP.
Why does an engineering control usually lower the risk more than an administrative one?
Because it acts on the hazard without depending on each person following a procedure every time.
08Further reading
- ISO. ISO 45001:2018. Occupational health and safety management systems. International Organization for Standardization; IRAM version in Spanish. The requirements of the management system and risk assessment.
- ISO. ISO 31000:2018. Risk management — Guidelines. International Organization for Standardization. The general principles of risk management, applicable to any organization.
- Trevor Kletz. HAZOP and HAZAN: Identifying and Assessing Process Industry Hazards. 4th ed., Institution of Chemical Engineers, 1999. The classic text on identifying and assessing process hazards.