Residual Risk, How You Can Calculate And Control It header image

2nd July, 2019

Residual Risk, How You Can Calculate And Control It

The main focus of risk assessment is to control the risks in your work activities. Of course, the best way to control risk is to eliminate it entirely. But you are not expected to eliminate all risks. There will always be some level of residual risk.

Definition and Meaning

- remaining after most of something has gone.

Residual risk is the remaining risk after your control measures are in place. There will always be some level of residual risk, but it should be as low as reasonably practicable. As in, as low as you can reasonably be expected to make it.

As low as reasonably practicable is a legal term, find out more in the ALARP principle with 5 real-world examples.

You are not expected to eliminate all risks, because, quite simply it would be impossible. You can't eliminate the risk of tripping on stairs, not unless we remove all the stairs in the world. Replace them with ramps? But even then, people could trip up the ramp simply because the floor level is rising. Even if we got rid of all stairs and ramps, and only had level flooring. People could still trip over their shoelaces. We could remove shoelaces, but then they could trip when their loose shoe falls off.

So, you see, in some cases, removing one risk can introduce others.

How to calculate residual risk

Residual risk can be calculated in the same way as any other risk. A risk is a chance that somebody could be harmed. And you can calculate this by:

Likelihood x Severity = Risk

So if it is highly likely that harm could occur, and that harm would be severe, then the risk is high. This wouldn't usually be an acceptable level of residual risk.

If the remaining risk is low, because it is unlikely anyone would be harmed, and that harm would be slight, then this could be an acceptable level of residual risk (based on the ALARP principle).

It's important to calculate residual risk, especially when comparing different control measures. If you are planning to introduce a new control measure, you need to know what it will control the hazards and reduce the residual risk as low, or lower than any current controls you have in place.

Comparison of option with best practice, and confirmation that residual risks are no greater than the best of existing installations for comparable functions.

Need help calculating risk? You can use our free risk assessment calculator to measure risks, including residual risk.

How to control residual risk

Residual risk should not be left uncontrolled. In fact, residual risk in its very definition is the risk that remains when the rest of the risk has been controlled. Residual risk should only be a small proportion of the risk level that would be involved in the activity if no control measures were in place at all.

In health and safety, you can look at residual risk as being the risk that cannot be eliminated. This could be that it just can't be removed, because there are no control measures that would prevent it. Or that to reduce that risk further you would introduce other risks. Or that it would be grossly disproportionate to control it.

To control residual risk to it's lowest possible level, you need to pick the best control measure, or measures, for a task.

The option, or combination of options, which achieves the lowest level of residual risk should be implemented, provided grossly disproportionate costs are not incurred.

While you are not expected to eliminate all risks, you are expected to reduce risk, as much as is reasonable. So, this means, when evaluating or deciding on controls, you should look at how you can get the lowest level of residual risk.

Remember, if the residual risk is high, ALARP has probably not been achieved.

How can you get the lowest level of residual risk?

Residual risk examples

The staircase example we gave earlier shows how there is always some level of residual risk. We can control it, by installing handrails, making sure that the stairs are kept clear and in good condition. Not allowing any trailing cables or obstacles to be located on the stairs. But some risk remains. There is a small chance that someone could trip up, or down the stairs. Hopefully, they will be holding the handrail and this will prevent a fall.

Another example is ladder work. Ladders are not a working platform, and not really designed for work at height. They don't have full edge protection, and it is difficult to carry out tasks safely from them. They are designed for access. However, for some short duration work, it may not be possible, or practical, to bring in other, safer work at height equipment. Scaffolding to change a lightbulb? So yes, there is a residual risk when using a ladder, your risk assessment should assess if it is as low as is reasonable for your task.

Working with sharp edges like scissors, knives or blades are always going to carry some element of residual risk. You can reduce the risk of cuts with training, supervision, guards and gloves, depending on what is appropriate for the task. But at some level, risk will remain.

Think of any task in your business. You will find that some risks are just unavoidable, no matter how many controls you put in place. And of course, if you try to eliminate it entirely, you might just find you can't carry out the task at all.

The key is, reducing risk as much as is reasonable. Controlling risks so that the residual risk remaining is so low, no one is likely to come to any significant harm.

Make sure you communicate any residual risk to your workforce. You can do this in your risk assessment.

Need help measuring risk levels? Use the free risk assessment calculator to list and prioritise the risks in your business.

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This article was written by Emma at HASpod. Emma has over 10 years experience in health and safety and BSc (Hons) Construction Management. She is NEBOSH qualified and Tech IOSH.

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