Introduction to Health and Safety at Work

5.3 
Forms of risk assessment
There are two basic forms of risk assessment.
A quantitative risk assessment attempts to measure 
the risk by relating the probability of the risk occurring 
to the possible severity of the outcome and then giving 
the risk a numerical value. This method of risk assess-
ment is used in situations where a malfunction could be 
very serious (e.g. aircraft design and maintenance or the 
petrochemical industry).
The more common form of risk assessment is 
the qualitative assessment, which is based purely on 
personal judgement and is normally defi ned as high, 
medium or low. Qualitative risk assessments are usually 
satisfactory since the defi nition (high, medium or low) 
is normally used to determine the time frame in which 
further action is to be taken.
The term ‘generic’ risk assessment is sometimes 
used and describes a risk assessment which covers 
similar activities or work equipment in different depart-
ments, sites or companies. Such assessments are often 
produced by specialist bodies, such as trade associ-
ations. If used, they must be appropriate to the particular 
job and they will need to be extended to cover additional 
hazards or risks.
5.4 
Some defi nitions
Some basic defi nitions were introduced in Chapter 1 and 
those relevant to risk assessment are reproduced here.
Electricity is an example of a high hazard since it 
has the potential to kill a person. The risk associated 
with electricity – the likelihood of being killed on coming 
into contact with an electrical device – is, hopefully, low.

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Risk assessment
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5.4.2 Occupational or work-related ill-health
This is concerned with those illnesses or physical and 
mental disorders that are either caused or triggered by 
workplace activities. Such conditions may be induced by 
the particular work activity of the individual or by activ-
ities of others in the workplace. The time interval between 
exposure and the onset of the illness may be short (e.g. 
asthma attacks) or long (e.g. deafness or cancer).
5.4.3 Accident
This is defi ned by the Health and Safety Executive as 
‘any unplanned event that results in injury or ill-health of 
people, or damage or loss to property, plant, mater ials 
or the environment or a loss of a business opportun-
ity’. Other authorities defi ne an accident more narrowly 
by excluding events that do not involve injury or ill-
health. This book will always use the Health and Safety 
Executive defi nition.