Introduction to Health and Safety at Work

Likelihood of occurrence
Likelihood level
Harm is certain or near certain to occur
High 3
Harm will often occur
Medium 2
Harm will seldom occur
Low 1
Severity of harm
Severity level
Death or major injury (as defi ned by
Major 3
RIDDOR)
3 day injury or illness (as defi ned by 
Serious 2
RIDDOR)
All other injuries or illnesses
Slight 1
Risk 
ⴝ
 Severity 
ⴛ
 Likelihood
Thus:
6–9 High risk
3–4 Medium risk
1–2 Low risk
It is possible to apply such methods to organizational 
risk or to the risk that the management system for health 
and safety will not deliver in the way in which it was 
expected or required. Such risks will add to the activity 
or occupational risk level. In simple terms, poor super-
vision of an activity will increase its overall level of risk. 
Whichever type of risk evaluation method is used, the 
level of risk simply enables a timetable of risk reduction 
to be formulated. The legal duty requires that all risks 
should be reduced to as low as is reasonably practicable.
5.9.4 Risk control measures
The next stage in the risk assessment is the control of 
the risk. In established workplaces, some control of risk 
will already be in place. The effectiveness of these con-
trols needs to be assessed so that an estimate of the 
residual risk may be made. Many hazards have had 
specifi c acts, regulations or other recognized standards 
developed to reduce associated risks. Examples of such 
hazards are fi re, electricity, lead and asbestos. The rele-
vant legislation and any accompanying approved codes 
of practice or guidance should be consulted fi rst and 
any recommendations implemented. Advice on control 
measures may also be available from trade associations, 
trade unions or employers’ organizations.
Where there are existing preventative measures 
in place, it is important to check that they are working 
properly and that everybody affected has a clear 
understanding of the measures. It may be necessary 
to strengthen existing procedures, for example, by the 
introduction of a permit to work system. More details on 
the principles of control are contained in Chapter 6.