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Assessing risk in engineering, work and life
Assessing risk in engineering, work and life

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1.3 Assessing risk

Engineers and other professionals need to be able to assess potential risks. This is the first stage in the process of deciding which risks are acceptable. This in turn allows priorities to be assigned to developing and implementing strategies to reduce risks.

  • What types of risk might you look at in a health and safety context?

    (Hint: think about your own workplace, places you visit and your home and the kinds of things that could go wrong.)

  • Perhaps the most obvious areas to consider are:

    • accidents – any unintended occurrence, regardless of whether it leads to damage or, if so, the type of damage
    • injuries – any harm (physical or non-physical) to a person due to an accident
    • illnesses – any detriment to a person’s well-being from accidents, exposure to harmful substances, poor working conditions, mental stress, etc. (generally speaking, illness covers longer-term issues than injuries, but the two areas do overlap)
    • near misses – any incident that could easily have resulted in harm (for example, a person trips but manages to avoid falling).

The first stage in assessing and managing risk is to identify the hazards. A hazard can be thought of as anything that might cause harm. There are many hazards both in the workplace and in life in general – for example, toxic or harmful chemicals, electricity, falling off a ladder or standing in an inappropriate area like a busy access road.


The risk associated with a particular hazard is the chance that somebody could be harmed, together with an indication of how serious the harm could be. Hence risk is often expressed in the form of an equation:

risk = severity of harm × likelihood of occurrence

A common way to use this equation is to rank both severity and likelihood on a scale of 1 to 5, and to set thresholds for action based on the result.

Table 2 shows some of the criteria that can be used in order to rank both the severity and the likelihood of a given risk, in order to use the risk equation.

Table 2 Risk assessment ranking
1 – Trivial, e.g. bruise or bump1 – Remote (almost never)
2 – Minor, e.g. small cut or abrasion2 – Unlikely (rare)
3 – Moderate, e.g. strain, sprain, off work <5 days3 – Possible (could occur but not common)
4 – Serious, e.g. fracture, incapacitation, off work >5 days4 – Likely (will probably occur once)
5 – Fatal or life-changing, e.g. permanent injury such as blindness or loss of mobility5 – Imminent (will occur regularly)

You may see the same idea expressed as a matrix, using a ‘traffic light’ system to indicate the acceptability of different risks. An example is shown in Figure 2, but note that different industries will use different criteria for what is acceptable.

Described image
Figure 2 Risk assessment matrix (in this example green represents low risk, yellow is medium risk and red is high risk)

As you can see, the overall risk is given by multiplying the two factors together. Once this has been done for a particular activity or process, a threshold for action is required. For example:

  • Low risk (1–8) – No immediate action is needed, but the activity should be reviewed if any changes occur.
  • Medium risk (9–12) – Safe systems of working and controls should be put in place to minimise risk as far as is reasonably practicable.
  • High risk (13–25) – The activity should not be allowed to take place. New controls or ways of working must be introduced to reduce the risk before the activity can be permitted to take place.