Residual Risk: What It Means and How to Record It Correctly in an Irish Risk Assessment

Residual risk is the risk that remains after control measures have been applied.

# Residual Risk: What It Means and How to Record It Correctly in an Irish Risk Assessment --- Residual risk is one of the most misunderstood concepts in health and safety risk assessment. Many contractors either ignore it entirely, treating the risk assessment as complete once control measures have been identified, or they misapply it by recording a residual risk level without properly considering whether the control measures they have identified are actually adequate to achieve that level. Understanding residual risk and recording it correctly is not just a matter of good practice. It is fundamental to the purpose of a risk assessment, which is to ensure that the risks in the workplace have been reduced to a level that is as low as reasonably practicable (ALARP). A risk assessment that does not address residual risk cannot demonstrate that this standard has been met. --- ## What Is Residual Risk? Residual risk is the level of risk that remains after all reasonably practicable control measures have been implemented. It is the risk that cannot be eliminated entirely, even after the employer has done everything that is reasonably practicable to reduce it. The concept of residual risk is inherent in the Irish legal standard of "so far as is reasonably practicable" (SFAIRP), which is the standard applied by the Safety, Health and Welfare at Work Act 2005. The Act does not require employers to eliminate all risk; it requires them to reduce risk to a level that is SFAIRP. The residual risk is the risk that remains after this standard has been met. --- ## The Risk Assessment Process and Residual Risk A properly conducted risk assessment involves the following steps in relation to residual risk. ### Step 1: Identify the Hazard and Assess the Inherent Risk The first step is to identify the hazard and assess the level of risk before any control measures are applied. This is sometimes called the "inherent risk" or "initial risk." It represents the worst-case scenario: what would the risk be if no controls were in place? The inherent risk is typically assessed using a risk matrix that combines the likelihood of harm occurring with the severity of the harm if it does occur. A common approach uses a 5x5 matrix with likelihood and severity each rated on a scale of 1 to 5, giving a risk score of 1 to 25. ### Step 2: Identify and Apply Control Measures The second step is to identify the control measures that will be implemented to reduce the inherent risk. Control measures should be selected using the hierarchy of control, which prioritises elimination and substitution over engineering controls, administrative controls, and personal protective equipment. ### Step 3: Assess the Residual Risk The third step is to assess the level of risk that remains after the control measures have been applied. This is the residual risk. It should be assessed using the same risk matrix as the inherent risk, so that the reduction in risk achieved by the control measures can be clearly seen. The residual risk assessment must be realistic. It must reflect the actual level of risk reduction that the control measures will achieve in practice, not the theoretical maximum reduction. For example, a control measure that requires workers to wear hearing protection will only reduce noise exposure to the extent that workers actually wear the protection correctly and consistently. If there is reason to believe that compliance will be poor, the residual risk should reflect this. ### Step 4: Determine Whether the Residual Risk Is ALARP The fourth step is to determine whether the residual risk is as low as reasonably practicable. If the residual risk is still unacceptably high after the identified control measures have been applied, additional control measures must be identified and implemented until the residual risk is ALARP. If the residual risk cannot be reduced to an acceptable level, the work should not proceed. --- ## How to Record Residual Risk in a Risk Assessment The residual risk should be recorded clearly in the risk assessment document. A typical format for recording residual risk in a construction risk assessment is as follows: | Hazard | Inherent Risk (L x S) | Control Measures | Residual Risk (L x S) | Acceptable? | |---|---|---|---|---| | Falls from height (scaffold) | 4 x 5 = 20 (High) | Full scaffold with double guardrail and toe boards; scaffold inspection before each shift; no work during high winds | 2 x 5 = 10 (Medium) | Yes | | Manual handling (concrete blocks) | 3 x 3 = 9 (Medium) | Mechanical handling where possible; team lifting for heavy items; manual handling training for all workers | 2 x 2 = 4 (Low) | Yes | | Excavation collapse | 4 x 5 = 20 (High) | Battering or shoring of all excavations over 1.25m; daily inspection by competent person; no workers in unsupported excavation | 2 x 5 = 10 (Medium) | Yes | In this format, the inherent risk and residual risk are both recorded, allowing the reader to see the level of risk reduction achieved by the control measures. The "Acceptable?" column records the assessor's judgement as to whether the residual risk is ALARP. --- ## Common Mistakes in Recording Residual Risk The following are the most common mistakes that contractors make when recording residual risk in construction risk assessments. ### Recording a Low Residual Risk Without Adequate Controls The most serious mistake is recording a low residual risk (for example, "Low" or a score of 2) without identifying control measures that are actually capable of achieving that level of risk reduction. This gives a false impression of safety and may lead workers to underestimate the actual level of risk. For example, recording a residual risk of "Low" for work at height on the basis that "workers will wear harnesses" is not adequate if the risk assessment does not also address the anchor points to which the harnesses will be attached, the inspection and maintenance of the harnesses, and the rescue procedure if a worker falls and is suspended in their harness. ### Not Distinguishing Between Inherent and Residual Risk Some risk assessments record only a single risk level, without distinguishing between the inherent risk and the residual risk. This makes it impossible to assess whether the control measures are adequate, because there is no baseline against which the effectiveness of the controls can be measured. ### Treating Residual Risk as a Fixed Number Residual risk is not a fixed number. It changes as control measures are implemented, maintained, or removed. A risk assessment that was accurate when it was prepared may become inaccurate if control measures deteriorate or are not implemented as described. The residual risk should be reviewed regularly to ensure it remains accurate. ### Using Unrealistic Likelihood Ratings A common error is to rate the likelihood of harm as "Very Unlikely" or "Rare" on the basis that the control measures will be implemented perfectly. In practice, control measures are not always implemented perfectly, and the likelihood rating should reflect the realistic probability of harm occurring, taking into account the possibility of human error, equipment failure, and other factors. --- ## Residual Risk and the ALARP Principle The ALARP principle requires employers to reduce risk to a level that is as low as reasonably practicable. A risk is ALARP when the cost (in terms of time, money, and effort) of further reducing the risk is grossly disproportionate to the benefit gained. In practice, determining whether a residual risk is ALARP requires a judgement about whether any additional control measures are available that would further reduce the risk, and whether the cost of implementing those measures is proportionate to the risk reduction they would achieve. For high-severity hazards (such as falls from height or contact with overhead power lines), the ALARP threshold is set very high: the employer must implement all reasonably practicable control measures, even if they are costly, because the potential consequences are so severe. For lower-severity hazards, a more proportionate approach is appropriate. --- ## Communicating Residual Risk to Workers Workers must be made aware of the residual risks associated with their work, not just the control measures they are required to follow. Understanding why a control measure is required, and what the consequences of not following it could be, helps workers to appreciate the importance of compliance and to make better decisions when unexpected situations arise. The residual risk should be communicated to workers as part of the site induction and through toolbox talks. For high-risk activities, the risk assessment and method statement should be discussed with the workers who will carry out the work before it begins. --- If you need help preparing or reviewing risk assessments for your construction business, or if you need advice on how to apply the ALARP principle to a specific hazard, Safety Check can assist. [Contact us](/contact) for practical guidance.