October 03 2019 0Comment


ALARP stands for “as low as reasonably practicable”, and is a term often used in the regulation and management of safety-critical and safety-involved systems. The ALARP principle is that the residual risk shall be reduced as far as reasonably practicable. In UK and NZ Health and Safety law, it is equivalent to SFAIRP (So Far As Is Reasonably Practicable).

For a risk to be ALARP, it must be possible to demonstrate that the cost involved in reducing the risk further would be grossly disproportionate to the benefit gained. The ALARP principle arises from the fact that infinite time, effort and money could be spent in the attempt of reducing a risk to zero. It should not be understood as simply a quantitative measure of benefit against detriment. It is more a best common practice of judgement of the balance of risk and societal benefit.


In this context, risk is the combination of the frequency (likelihood) and the consequence of a specified hazardous event.

The following factors are likely to be considered when deciding whether or not a risk has been reduced as far as reasonably practical.

  • Health and safety guidelines and codes of practice
  • Manufacturer’s specifications and recommendations
  • Industry practice
  • International standards and laws
  • Suggestions from advisory bodies
  • Comparison with similar hazardous events in other industries

Cost of further measures would be disproportionate to the risk reduction they would achieve

Another factor that often comes into the ALARP principle is the cost of assessing the improvement gained in an attempted risk reduction. In extremely complex systems, this can be very high, and could be the limiting factor in practicability of risk reduction, although according to HSE guidance, cost alone should never be a justification for taking extra safety risks.

Determining that a risk has been reduced to ALARP involves an assessment of the risk to be avoided, of the sacrifice (in money, time and trouble) involved in taking measures to avoid that risk, and a comparison of the two. This is a cost–benefit analysis.

Why do I need to know about ALARP?

Because ALARP is fundamental to the work of the whole organization, it is important that everyone, whatever their role, knows about it. Here are some specific reasons for you to know about ALARP and its relationship with good practice, but this is not an exhaustive list.

  • Policy makers and those engaged in Programme delivery need to know about ALARP because when you make proposals for HSC/E action to control health or safety risks, you need to make sure that, as far as possible, those controls will reduce the risks to employees (or other people, as the case may be) ALARP.
  • Enforcers need to know about ALARP because you will have to decide whether duty-holders have reduced their risks ALARP and so have complied with the law.
  • Technical specialists in HSE need to know about ALARP because you advise colleagues in HSE about whether control measures reduce risks ALARP and you help identify standards of risk control that are ALARP.



They can be used to map risks, by indicating high (normally unacceptable) risks at the upper/wider end and low (broadly acceptable) risks at the lower/narrower end. The region in between is sometimes called the ALARP region. However, this is misleading because ALARP refers to the principle of testing further risk reduction against the cost of this reduction effort, regardless of tolerability, and applies to all regions. A better name is the ‘tolerable region’, because risks in this region can sometimes be tolerated, if it can be shown that reasonable mitigations have been put in place.

Origin in UK law

The term ALARP arises from UK legislation, particularly the Health and Safety at Work etc. Act 1974, which requires “Provision and maintenance of plant and systems of work that are, so far as is reasonably practicable, safe and without risks to health”. The phrase So Far As is Reasonably Practicable (SFARP) in this and similar clauses is interpreted as leading to a requirement that risks must be reduced to a level that is As Low As is Reasonably Practicable (ALARP).

The key question in determining whether a risk is ALARP is the definition of reasonably practicable. This term has been enshrined in the UK case law since the case of Edwards v. National Coal Board in 1949. The ruling was that the risk must be significant in relation to the sacrifice (in terms of money, time or trouble) required to avert it: risks must be averted unless there is a gross disproportion between the costs and benefits of doing so.

Including gross disproportion means that an ALARP judgement in the UK is not a simple cost benefit analysis, but is weighted to favor carrying out the safety improvement. However, there is no broad consensus on the precise factor that would be appropriate.

Use outside the UK

Outside the UK the ALARP principle is often not used; instead standards and ‘good engineering practice’ are adhered to, and legislation tends to require absolute levels of safety.

The term ALARA, or “as low as reasonably achievable” is used interchangeably in the United States of America, almost exclusively in the field of radiation protection.

Where the ALARP principle is used, it may not have the same implications as in the UK, as “reasonably practicable” may be interpreted according to the local culture, without introducing the concept of gross dis-proportionality.

Starfish Medical, a company focusing on medical device contract manufacturing and product development, through the Medical Device Directive of Canada is undergoing extensive consideration of the transfer of ALARP to AFAP (“As Far As Possible”) specifically for the regulation of risk of medical devices. The ALARP concept contains legal interpretation of the regulatory process that promotes financial consideration in higher regard than of the requirements of safety and performance of medical devices.

Contradicting this approach, AFAP requires that all ventures of safety must be addressed in the intent of the consumer and effectiveness of the product rather than capital gain of the corporation. Under AFAP standards there are two defined justifications for the lack of implementation of risk-preventative measures. The first indicates that the additional risk control will not provide additional support for the system, such as an additional alarm when a previous alarm is functioning. The second states that a risk control system does not have to be implemented if there is a more effective risk control that cannot be simultaneously executed due to various scenarios such as spatial boundaries. By implementing this new standard of risk mitigation, companies must demonstrate that they have considered and implemented all necessary means of addressing risk of a product or developed system.

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