2.3 HIRARC and the General Principles of Prevention
Key Takeaways
The DOSH HIRARC Guidelines 2008 define hazard as a source or situation with a potential for harm in terms of human injury or ill health, damage to property, damage to the environment or a combination of these.
In the HIRARC 2008 risk matrix, risk equals likelihood multiplied by severity, each rated 1 to 5: scores of 15 to 25 are High, 5 to 12 are Medium and 1 to 4 are Low.
A High risk under HIRARC 2008 requires immediate action to control the hazard as detailed in the hierarchy of control, documented on the assessment form with a completion date.
HIRARC 2008 says the assessment should be reviewed every three years or whenever there are changes in the process or activities.
The First Schedule of CDM 2024 lists nine general principles of prevention, beginning with avoiding risks and including giving collective protective measures priority over individual measures.
The legal hook
Before Act A1648, risk assessment was implied by the general duties in section 15. Since 1 June 2024, section 18B of OSHA 1994 requires every employer, self-employed person and principal to:
- conduct a risk assessment of the risks to anyone who may be affected by its undertaking, and
- implement whatever control the assessment shows is needed.
CDM 2024 adds that designers, the principal designer, the principal contractor and contractors must apply the general principles of prevention (First Schedule). Contractors must give workers the risk information identified by the section 18B assessment (regulation 17(2)(c)).
The DOSH Guidelines for HIRARC 2008 are the method NIOSH teaches. They also matter for Paper 2B: the presentation guideline tells candidates to present HIRARC "with reference to the HIRARC Guidelines 2008", and it is the largest single item in the marking scheme (20 of 100 marks).
Definitions in HIRARC 2008
| Term | Definition (HIRARC 2008, section 2.0) |
|---|---|
| Hazard | A source or a situation with a potential for harm in terms of human injury or ill health, damage to property, damage to the environment or a combination of these |
| Hazard identification | Identification of the undesired events that lead to the hazard materialising, and the mechanism by which they could occur |
| Risk | A combination of the likelihood of a hazardous event occurring within a specified period or circumstances and the severity of injury or damage it causes |
| Risk assessment | The process of evaluating the risks to safety and health arising from hazards at work |
| Hazard control | The process of implementing measures to reduce the risk associated with a hazard |
| Hierarchy of control | The established priority order for the types of measures used to control risks |
| Risk management | The total procedure of identifying a hazard, assessing the risk, putting control measures in place and reviewing the outcomes |
Many trainers also use the word danger to describe a person's exposure to a hazard: an open floor edge is a hazard, and a worker standing next to it unprotected is in danger. Note that HIRARC 2008 itself does not define "danger". Quote the guideline's own definitions when a question asks for them.
The HIRARC process
HIRARC 2008 (section 4.3) describes four simple steps, supported by consultation between employer and worker representatives and by review:
- Classify work activities. Group them by area, stage or defined task, not too big ("build the tower") and not too small ("tighten one bolt"). Example: "erect independent scaffold, Block B east façade".
- Identify hazards. HIRARC groups them as health hazards (for example silica dust, noise, heat), safety hazards (falls, collapse, struck-by, electrocution) and environmental hazards (spills, silt runoff).
- Assess the risk. Estimate likelihood and severity, taking existing controls into account, and read off the risk level.
- Control the risk. Prepare and implement a risk control action plan using the hierarchy of control. Assign a responsible person and a target date, then reassess the residual risk.
Useful identification techniques on a construction site include:
- walk-through inspections
- task or job hazard analysis
- method statements
- checklists
- worker and toolbox feedback
- near-miss and accident records
- safety data sheets and manufacturers' manuals
- design information from the principal designer, such as the pre-construction information and health and safety file
Rating likelihood and severity
Table A: likelihood (HIRARC 2008)
| Rating | Likelihood | Description |
|---|---|---|
| 5 | Most likely | The most likely result of the hazard or event being realised |
| 4 | Possible | Has a good chance of occurring and is not unusual |
| 3 | Conceivable | Might occur at some time in future |
| 2 | Remote | Has not been known to occur after many years |
| 1 | Inconceivable | Is practically impossible and has never occurred |
Table B: severity (HIRARC 2008)
| Rating | Severity | Description |
|---|---|---|
| 5 | Catastrophic | Numerous fatalities, irrecoverable property damage and productivity |
| 4 | Fatal | Approximately one single fatality; major property damage if the hazard is realised |
| 3 | Serious | Non-fatal injury, permanent disability |
| 2 | Minor | Disabling but not permanent injury |
| 1 | Negligible | Minor abrasions, bruises, cuts, first-aid type injury |
The risk matrix and required action
Risk = Likelihood (L) x Severity (S).
| L \ S | 1 Negligible | 2 Minor | 3 Serious | 4 Fatal | 5 Catastrophic |
|---|---|---|---|---|---|
| 5 Most likely | 5 M | 10 M | 15 H | 20 H | 25 H |
| 4 Possible | 4 L | 8 M | 12 M | 16 H | 20 H |
| 3 Conceivable | 3 L | 6 M | 9 M | 12 M | 15 H |
| 2 Remote | 2 L | 4 L | 6 M | 8 M | 10 M |
| 1 Inconceivable | 1 L | 2 L | 3 L | 4 L | 5 M |
| Risk | Score | Action required by HIRARC 2008 (Table D) |
|---|---|---|
| High | 15–25 | Immediate action to control the hazard as detailed in the hierarchy of control, documented on the risk assessment form with a completion date. The person responsible for action and follow-up must be identified |
| Medium | 5–12 | A planned approach to controlling the hazard, with temporary measures if required, documented with a completion date |
| Low | 1–4 | May be considered acceptable and further reduction may not be necessary. If it can be resolved quickly and efficiently, control it and record it |
On site, "immediate action" for a High risk usually means the activity does not start, or is stopped, until controls have brought the risk down. That is the practical way to meet the duty, and it is what the SSS's stop-work authority is for.
The hierarchy of control
HIRARC 2008 (section 5) prefers controls at the source, then along the path to the worker, and only then at the worker.
| Level | HIRARC 2008 examples | Construction examples |
|---|---|---|
| Elimination | Get rid of the hazardous job, tool, process, machine or substance | Assemble roof trusses at ground level and lift them as one unit |
| Substitution | Do the same work in a less hazardous way | Water-based instead of solvent-based coatings; a mechanical breaker on a long-reach arm instead of hand-held jackhammers |
| Engineering control | Redesign, isolation, automation, barriers, absorption, dilution | Guardrails and floor-opening covers; local exhaust or water suppression on cutting saws; acoustic enclosures on generators |
| Administrative control | Safe work procedures, supervision and training, job rotation, housekeeping and maintenance, hygiene | Permit-to-work; exclusion zones; rotating breaker operators; daily housekeeping |
| Personal protective equipment | Last resort, used with the other levels | Harness and lanyard where edge protection is impracticable; respirators; hearing protection |
USECHH regulation 15 and the Noise Exposure Regulations 2019 apply the same order to chemicals and noise.
The general principles of prevention (CDM 2024, First Schedule)
- Avoid risks.
- Evaluate the risks that cannot be avoided.
- Combat risks at source.
- Adapt the work to the individual, especially in the design of workplaces, the choice of plant and the choice of working and production methods, to reduce monotonous work and work at a predetermined rate and their effect on health.
- Adapt to technical progress.
- Replace the dangerous by the non-dangerous or the less dangerous.
- Develop a coherent overall prevention policy covering technology, organisation of work, working conditions, social relationships and the influence of factors related to the working environment.
- Give collective protective measures priority over individual protective measures.
- Give appropriate instructions to workers.
Principle 8 is the legal basis for preferring guardrails and nets (collective) over harnesses (individual). Principle 4 links HIRARC to ergonomics and human factors.
Writing a HIRARC entry that scores
| Field | Weak entry | Strong entry |
|---|---|---|
| Activity | "Formwork" | "Erect beam formwork at Level 8 perimeter, grid A–F" |
| Hazard | "Fall" | "Fall of person from unprotected slab edge (about 28 m)" |
| Existing control | "PPE" | "Harness issued; no anchorage; no edge protection" |
| L x S | "High" | "L4 Possible x S4 Fatal = 16, High" |
| Additional control | "Be careful" | "Install proprietary edge protection before work starts (engineering); permit for edge work; SSS check before start (administrative); harness only while fitting edge protection" |
| Responsible person and date | blank | "Site engineer; before 07:30, 24 Oct 2026" |
| Residual risk | blank | "L1 x S4 = 4, Low" |
When to review
HIRARC 2008 (section 6.2) says to "review HIRARC every three years or whenever there are changes in process or activities". On a construction project, changes happen constantly: new trades, new plant, weather, design changes and incidents. In practice the activity HIRARC is reviewed far more often than every three years, and every review must be recorded.
An SSS rates a perimeter formwork task as Likelihood 4 (Possible) and Severity 4 (Fatal) under the HIRARC 2008 matrix. What is the risk level and the required action?
16, High: immediate action by the hierarchy of control, with a completion date
8, Medium: a planned approach, with temporary measures until the next project phase
12, Medium: temporary measures only, with no documentation required
16, Low: acceptable as it is, because every worker at the edge wears a harness
According to the DOSH HIRARC Guidelines 2008, how often should a HIRARC be reviewed at minimum?
Every month, at the site's safety and health committee meeting
Every three years, or when the process or activities change
Only after a fatal accident
Every five years, or whenever the Director General directs a review
Which principle in the First Schedule of CDM 2024 most directly supports choosing perimeter guardrails over issuing harnesses to each worker?
Adapt to technical progress by buying the newest harness designs
Give appropriate instructions to workers on how to use their harnesses
Evaluate the risks that cannot be avoided
Give collective protection priority over individual protection
Sections you finish are checked off in the contents.