The As Low As Reasonably Practicable (ALARP) principle is key to the tolerability of risk framework used by the United Kingdom Health and Safety Executive (UK HSE) in the regulation of hazards in industry and by companies in managing the risks of hazardous facilities.
The As Low As Reasonably Practicable principle provides a sensible basis for managing process risks. It embodies several concepts.
First, risks for processes can be partitioned into three regions:
- Unacceptable risks that cannot be justified except under extraordinary circumstances.
- Tolerable risks that are considered acceptable if further risk reduction is impractical, i.e., the benefit does not outweigh the impact.
- Broadly acceptable risks that are so low as not to be of concern.
Second, as risk decreases, the proportional benefit of risk reduction diminishes.
Third, efforts to reduce risk should be continued until the incremental sacrifice is grossly disproportionate to the value of the incremental risk reduction achieved. Incremental sacrifice is defined in terms of cost, time, effort, or other expenditures of resources.
Application of the ALARP principle involves specifying two sets of risk tolerance criteria. The first set of criteria, corresponding to the dividing line between the unacceptable and tolerable regions, usually called the maximum tolerable risk, is a minimum requirement that must be met. The second set of criteria, corresponding to the dividing line between the tolerable and broadly acceptable regions, usually called the broadly acceptable risk, is a goal which may not be reached but towards which progress must be made until risk reduction measures involve grossly disproportionate sacrifices. The residual risk, that is the risk remaining after controls have been implemented, should fall either in the broadly acceptable region, or near the bottom of the tolerable region. The ALARP principle can be incorporated into both qualitative and quantitative risk analysis.
Establishment of risk acceptance criteria
The risk acceptance criteria (RAC) serve as the foundation for risk acceptance decisions.
Risk acceptance criteria were established in a variety of ways by regulatory authorities around the world.
In general, the criteria can be classified according to three ‘pure’ criteria. Regulators have
either used these ‘pure’ criteria on their own or have used them as building blocks to create new criteria. They are (UK HSE, 2001):
- Equity-based — the notion is that everyone has an unalienable entitlement to certain levels of protection. This frequently translates into establishing a limit that represents the greatest level of risk to which no single person can be exposed. If the risk exceeds this limit and further control efforts are ineffective, the risk is considered unacceptable.
- Utility-based — this approach measures risk reduction against cost. It compares the monetary value of benefits (e.g., statistical lives saved, life-years extended) to the cost of a risk’s prevention method. It also necessitates a certain level of equilibrium between the two.
- Technology-based – approach reflects the idea that application of state-of-the-art
technology gives an acceptable level of risk.
Methodology
Generally, the three main methods that are either mandated or recommended to determine whether risks are ALARP are
- good practices and standards,
- cost-benefit analysis through first principles, and
- the safety case.
Good practices involve following existing codes, standards, and accepted industry practices to ensure that the safety of a facility is acceptable.
Cost-benefit analysis is a risk-based methodology that determines whether a risk is ALARP by weighting the cost of reducing risk against the risk itself.
The safety case is a practice by which each individual hazard is examined, controls are implemented, and then over the operational time of the facility, hazards and controls are maintained so that the safety remains ALARP.
Process
The overall process by which risk management is performed under the ALARP is as follows:
- Identify the hazards
- Decide who might be harmed and how
- Evaluate the risks and decide on the precautions
- Record significant findings
- Review risk assessment and update if necessary
In general, ALARP as defined by the UK HSE puts the burden of responsibility on duty holders to find every reasonable safety measure, but also gives them the flexibility to decide whether such measures are necessary based upon a flexible but stringent methodology of analysis.
The rigor of the analysis is not high unless there is a high degree of hazard, or if the case is complex or novel. Even when cost benefit analysis is required, a high degree of rigor is not always necessary.
