Risk assessment is the core of a safety system: find the hazards, judge the risk, and decide what to do about it. Done well, it points effort at the risks that matter and at controls that work. Done badly, it produces a binder of scores and no change.
This guide explains hazard, harm, and risk; when and with whom to assess; a seven-step process; how to find hazards; how to rate risk with a matrix, and why a matrix is only a thinking tool; the hierarchy of controls; and how to record, communicate, and review. A worked register of eight hazards at an illustrative plant shows the result, with every score calculated.
Scores and thresholds in the example are illustrative. Agree your own scales with the people who do the work.
Before You Start
Hazard, Harm, and Risk
| Term | Meaning | Example |
|---|---|---|
| Hazard | Something with the potential to cause harm | A press that can close on a hand |
| Harm | The injury or illness that could result | A crushed hand |
| Exposure | How often and for how long people are near the hazard | Loading the press 400 times a shift |
| Risk | The combination of the likelihood of harm and its severity | Likely that a hand is caught, with severe results |
| Control | Something that eliminates or reduces the risk | A light curtain that stops the press |
| Residual risk | The risk that remains after the controls | Low, if the curtain works and is maintained |
A hazard does not change unless you remove or change the thing itself. Risk changes with controls and exposure. Risk assessment is the discipline of finding hazards, judging the risk, and deciding what to do, in that order.
When and Who
- When: before new or changed work, equipment, materials, or layouts; after an incident, near miss, or audit finding; when the rules change; and on a regular schedule for existing risks.
- Who: a small team that includes people who do the work, their supervisor, and someone with safety knowledge. People who do the job know what really happens, and people who did not design it see what the designers missed.
- What: routine work, non-routine work (maintenance, cleaning, jams, start-up and shutdown), emergencies, contractors, visitors, and people who may be especially vulnerable.
The Process
- Prepare and scope. Decide what is being assessed, who is on the team, and what information is needed: incident history, manuals, safety data sheets, standards, and layouts.
- Identify hazards. Walk the area, watch the work, talk to the people, review incidents and near misses, and use hazard checklists.
- Decide who could be harmed and how. Include operators, maintenance, cleaners, visitors, and contractors.
- Assess the risk. Judge severity and likelihood with the controls that exist today, and rate the risk.
- Decide on controls. Work down the hierarchy of controls. Do not stop at training and a warning sign.
- Record and act. Write the assessment, assign owners and dates, put controls in place, and tell the people affected.
- Verify and review. Check that controls were put in place and work, re-score the residual risk, and review when anything changes.
Finding Hazards: What to Look For
| Category | Examples |
|---|---|
| Mechanical | Moving parts, pinch points, rotating shafts, presses, cutting, flying fragments |
| Energy and electrical | Stored energy, hydraulic or pneumatic release, live parts, arc flash |
| Slips, trips, and falls | Wet or uneven floors, clutter, stairs, work at height, ladders |
| Struck by or against | Forklifts, falling objects, swinging loads, moving vehicles |
| Chemical | Solvents, acids, fumes, dust, welding fume, gases |
| Fire and explosion | Flammable liquids, combustible dust, ignition sources, hot work |
| Physical agents | Noise, vibration, heat, cold, radiation |
| Ergonomic | Heavy lifting, repetitive motion, awkward posture, long standing |
| Biological | Bacteria, mold, animals, bodily fluids |
| Psychosocial and organizational | Fatigue, shift patterns, stress, violence, lone working, time pressure |
Use several sources: a walk of the area, a review of incidents and near misses, safety data sheets, equipment manuals, relevant standards, and the knowledge of the workers. For complex processes, structured methods such as FMEA or HAZOP find failure modes systematically; see the FMEA guide.
Rating Risk: The Matrix and Its Limits
Most organizations rate risk on a matrix of severity against likelihood. A five-by-five matrix gives a score from 1 to 25, and bands that tell you what to do.
| Score | Severity: the worst credible harm | Likelihood: how often it could happen |
|---|---|---|
| 1 | Minor: first aid | Rare |
| 2 | Moderate: medical treatment | Unlikely |
| 3 | Serious: lost time or restricted work | Possible |
| 4 | Major: permanent injury or illness | Likely |
| 5 | Catastrophic: fatality or multiple serious injuries | Almost certain |
| Band | Score | Typical action |
|---|---|---|
| Extreme | 17 to 25 | Stop. Do not start or continue until the risk is reduced |
| High | 10 to 16 | Act now. Do not proceed without strong controls and senior review |
| Medium | 5 to 9 | Plan and carry out controls within a set time; keep monitoring |
| Low | 1 to 4 | Accept with routine controls; keep watching for change |
The matrix is a thinking tool, not a measurement. Scores are ordinal and depend on the people who give them, similar scores can hide very different risks, and the matrix compresses the range of outcomes. Research on risk matrices, such as Louis Cox’s 2008 paper “What’s Wrong with Risk Matrices?”, shows these limits. Use the matrix to structure a discussion by a team and to rank work, define each level with examples for your site, score the worst credible harm, and treat any serious-injury hazard seriously whatever its score.
Controlling Risk: The Hierarchy of Controls
| Level | What it does | Example | Reliability |
|---|---|---|---|
| Elimination | Removes the hazard | Stop manual lifting by redesigning the process so parts arrive at the machine | Highest: the hazard is gone |
| Substitution | Replaces it with something less hazardous | A water-based cleaner instead of a solvent | High |
| Engineering controls | Isolates people from the hazard | Fixed guards, interlocks, light curtains, ventilation, lift assists | High: works without human action |
| Administrative controls | Changes how people work | Procedures, training, job rotation, signs, permits | Lower: depends on people every time |
| PPE | Protects the person | Gloves, glasses, respirators, hearing protection | Lowest: depends on fit, use, and the hazard staying within the equipment limits |
- Aim for the top. Ask first whether the hazard can be eliminated, then substituted, then engineered out.
- Combine controls. Serious hazards usually need more than one, with at least one at an upper level.
- Do not stop at training and signs. They are controls of last resort for serious hazards, not first choices.
- Consider new hazards. A control can create new hazards, such as a guard that makes cleaning awkward, so check.
- Design it in. The cheapest time to remove a hazard is before the equipment or process exists, which is the idea of prevention through design.
Worked Example: A Risk Register at Riverside Plant
Riverside Plant, an illustrative 140-employee metal fabrication and assembly plant, assessed eight hazards with teams of operators, supervisors, and the safety coordinator. All figures are illustrative.
| # | Hazard | Area | Initial (S × L) | Main control | Level | Residual (S × L) |
|---|---|---|---|---|---|---|
| 1 | Press closes on the operator's hands | Press line | 5 × 3 = 15 (High) | Light curtain and two-hand control | Engineering | 5 × 1 = 5 (Medium) |
| 2 | Forklift and pedestrian conflict | Shipping dock | 5 × 3 = 15 (High) | Physical barriers and a separate pedestrian walkway | Engineering | 5 × 1 = 5 (Medium) |
| 3 | Unexpected start-up during maintenance | Machining | 5 × 2 = 10 (High) | Lockout/tagout procedure and audits | Administrative | 5 × 1 = 5 (Medium) |
| 4 | Manual lifting of 25 kg parts | Assembly | 3 × 4 = 12 (High) | Lift assists and a lifting height standard | Engineering | 3 × 2 = 6 (Medium) |
| 5 | Solvent vapor in the parts washer | Parts washing | 3 × 3 = 9 (Medium) | Substitute a low-VOC cleaner; local exhaust | Substitution | 2 × 2 = 4 (Low) |
| 6 | Noise above the action level at the saws | Cutting | 3 × 4 = 12 (High) | Quieter blades and enclosures; hearing protection | Engineering | 3 × 2 = 6 (Medium) |
| 7 | Wet floor at the wash station | Parts washing | 2 × 4 = 8 (Medium) | Drainage and non-slip flooring; spill procedure | Engineering | 2 × 2 = 4 (Low) |
| 8 | Welding fume | Weld cell | 4 × 3 = 12 (High) | Fume extraction at the source | Engineering | 4 × 1 = 4 (Low) |
Results. Before the controls, 6 hazards were High and 2 were Medium. After, 3 are Low and 5 are Medium, with none High. The average reduction in risk score is 57%. 7 of the 8 main controls are at the top three levels of the hierarchy, and one is administrative (lockout/tagout).
Record your own assessments in the Risk Assessment Register, or build one job at a time with the JHA and Risk Assessment Builder.
Risk Assessment, JHA, FMEA, and HAZOP
| Method | Best for | Level of detail | See |
|---|---|---|---|
| Workplace risk assessment | Hazards across an area, process, or site | Hazard by hazard, with scores | This guide |
| Job hazard analysis | One job, step by step | Step by step | Job Hazard Analysis |
| FMEA / HFMEA | Failure modes of a process or design, with detection | Failure mode by failure mode | FMEA; HFMEA |
| HAZOP and process hazard analysis | Chemical and process plant, by deviation from design intent | Node by node, by guide word | Process Safety and MoC |
Recording, Communicating, and Reviewing
- Record the hazards, who is exposed, the controls, the risk scores before and after, the owner, the due date, and the review date.
- Communicate the findings to the people who do the work, and make sure they know the controls and why they matter.
- Verify that controls are in place and effective, by inspection and audit. A control that is on paper only is not a control.
- Review after any incident or near miss, when the work or equipment changes, when the rules change, and on a regular schedule. Use management of change so that changes are assessed before they happen.
Common Mistakes
Assessing at a Desk
The people who do the work are not involved, so real hazards are missed.
Training as the Main Control
Procedures, signs, and training for serious hazards, with no engineering control.
False Precision
Treating a matrix score as a measurement and arguing over a point.
Scoring the Best Case
Rating the risk as if every control always works.
Never Reviewing
Assessments filed and forgotten while the work changes.
No Follow-Through
Actions without owners, dates, or verification.
Self-Assessment Questions
- Have we assessed all of our high-risk and non-routine tasks, with the people who do them?
- Do we rate risk with agreed scales and examples, and do we treat serious-injury hazards seriously whatever the score?
- Do our controls come from the top of the hierarchy where possible, or do we rely on training and PPE?
- Do we verify that controls are in place and work, and re-score the residual risk?
- Do we review assessments after incidents and changes?
Workplace Risk Assessment: Frequently Asked Questions
What is the difference between a hazard and a risk?
A hazard is something that has the potential to cause harm, such as a moving press or a toxic chemical. Risk is the combination of how likely the harm is and how severe it would be, given the controls and the exposure. A hazard can have a low risk if it is well controlled.
What is the hierarchy of controls?
A ranking of ways to control a hazard, from most to least effective: elimination, substitution, engineering controls, administrative controls, and personal protective equipment. Higher controls are more reliable because they depend less on people doing the right thing every time. NIOSH and many standards use it.
Are risk matrices reliable?
They are useful for structuring a team discussion and ranking work, but they are not measurements. Scores are subjective and ordinal, and different risks can get the same score. Use agreed scales with examples, score the worst credible harm, and treat serious-injury hazards seriously whatever the score.
How often should risk assessments be reviewed?
Review them after any incident or near miss, when work, equipment, materials, or rules change, and on a regular schedule, commonly once a year for high-risk tasks. Use management of change to assess changes before they happen.
Who should do the assessment?
A small team that includes people who do the work, their supervisor, and someone with safety knowledge, with experts for specialized hazards. Workers know what really happens, and a mixed team sees more than any one person.
Sources and Further Reading
- ISO 45001:2018, clause 6.1 on actions to address risks and opportunities, and hazard identification (check current edition).
- National Institute for Occupational Safety and Health, Hierarchy of Controls and Prevention through Design materials; ANSI/ASSP Z590.3.
- UK Health and Safety Executive, Five Steps to Risk Assessment and Managing for Health and Safety (HSG65).
- ISO 31000, Risk management: guidelines; IEC 31010, Risk assessment techniques.
- Louis Anthony Cox Jr., “What’s Wrong with Risk Matrices?” Risk Analysis, 28(2), 2008.
- US Occupational Safety and Health Administration, Recommended Practices for Safety and Health Programs (2016).