Book extract
Revised: Health and safety: risk
management
by Dr Tony Boyle
£57 softback 556 pages
ISBN 978 0 901357 41 0
Hierarchies of risk control measures
In any given set of circumstances, some risk control measures
will be 'better' than others and it is obviously preferable to use
the 'best' option. However, there are various different criteria
which can be used to define 'best', including:
- The number of people protected by the risk control measure. In
general, it is better to use a risk control measure which will
protect everyone who could be exposed to the hazard, rather than
relying on individuals to provide their own protection. For
example, it is better to put a soundproof enclosure around a noisy
machine than to expect everyone who might be exposed to the
machine's noise to wear hearing protection.
- The extent to which the continuing effectiveness of the risk
control measure relies on human behaviour. In general, it is
preferable to have risk control measures which, apart from any
necessary maintenance, operate without human intervention. When a
risk control measure relies on the actions of people, it is
inevitable that on some occasions it will not be used, either
deliberately or inadvertently.
- The extent to which the risk control measure requires testing,
maintenance, cleaning, replacement and so on. All of these required
activities rely on human intervention and can, therefore, fail.
This reduces the likelihood that the risk control measure will
continue to be effective.
- The cost of the risk control measure. Ideally, the cost should
be calculated over the whole of the time for which risk control is
required, since some risk control measures have a low installation
cost but are expensive to maintain, while others have higher
installation costs but are cheaper to maintain. This aspect of risk
control measures is dealt with in more detail later in this
chapter.
- And, last but not least, the extent to which the risk control
measure reduces the risk. Ideally a risk control measure, or
combination of measures, will reduce the risk to near zero, but
this may not be achievable in practice.
When deciding on the 'best' risk control measures, we need to
arrive at a compromise between all the demands listed above, since
they are often in competition. However, a critical issue for a
measure's long-term effectiveness is the extent to which it relies
on human beings continuing to carry out particular activities. For
this reason, a number of risk control hierarchies have been
developed which are based on this criterion. Six of these
hierarchies are described next.
Hierarchy 1: Technical, procedural and behavioural
This hierarchy has three categories:
1. Technical risk control measures,
including machinery guarding, various forms of fencing, and
different types of ventilation. In general, these types of measure
can be designed and installed so that they have the minimum
reliance on people doing what they are supposed to do.
2. Procedural risk control measures, including
systems of work and maintaining plant, equipment and so on in a
safe condition. Where the procedures are well designed and their
implementation is effectively monitored, these measures can be
successful, but they do rely on, for example, people keeping to
work procedures and remembering to carry out the necessary
maintenance work.
3. Behavioural risk control measures,
including information and training. These measures rely for their
effectiveness on a number of things, including the appropriateness
of the information or training, the extent to which it is
understood, and the extent to which this understanding is put into
practice. As a category, therefore, it is the one which is most
prone to failure as a result of people not doing what they are
supposed to do.
Hierarchy 2: Elimination to PPE
This hierarchy has six categories:
1. Eliminate hazard at source –
for example:
- use a non-hazardous substance instead of a hazardous one
- stop using a noisy machine.
2. Reduce hazard at source – for
example:
- use a substance less hazardous than the one used at
present
- replace a noisy machine with a quieter one.
3. Remove person from hazard – for
example:
- use unattended robots for paint spraying
- do not allow people to work near noisy machines.
4. Contain hazard by enclosure –
for example:
- do all painting in a proper, enclosed painting bay
- put soundproofing round a noisy machine.
5. Reduce employee exposure – for
example:
- four people exposed for two hours each, not one person for
eight hours – applies to exposure to substances or noise.
6. PPE – for example:
- gloves or goggles for substances and hearing protection for
noise.
Hierarchy 3: HSG65
The following extract is from HSG65's advice on risk control
hierarchies:
The following is a summary of the preferred hierarchy of risk
control principles:
- Eliminate risks by substituting the dangerous by the inherently
less dangerous, eg: use less hazardous substances;
- substitute a type of machine which is better guarded to make
the same product;
- avoid the use of certain processes, eg by buying from
subcontractors.
- Combat risks at source by engineering controls and giving
collective protective measures priority, eg:
- separate the operator from the risk of exposure to a known
hazardous substance by enclosing the process;
- protect the dangerous parts of a machine by guarding;
- design process machinery and work activities to minimise the
release of, or to suppress or contain, airborne hazards;
- design machinery which is remotely operated and to which
materials are fed automatically, thus separating the operator from
danger areas.
- Minimise risk by:
- designing suitable systems of work;
- using personal protective clothing and equipment – this should
be only be used as a last resort.
The hierarchy reflects the fact that eliminating and controlling
risk by using physical engineering controls and safeguards is more
reliable than relying solely on people.
Hierarchy 4: Airborne hazardous substances
1. There are various hierarchies which
have been devised specifically for controlling risks from airborne
hazardous substances. They can be summarised as follows:
2. eliminate the need for the hazardous
substances by, for example, redesigning the process
3. substitute a less hazardous substance
for the substance currently being used
4. isolate or enclose the process in
which the hazardous substance is used
5. local exhaust ventilation
6. general or dilution ventilation
7. PPE
8. reduce exposure time
9. personal hygiene (for example a ban on
eating and drinking in contaminated areas, providing washing
facilities, and disposing of contaminated PPE).
Hierarchy 5: Management Regulations
The hierarchy given below is quoted from the UK's Management of
Health and Safety at Work Regulations 1999. Where an employer
implements any preventive and protective measures, he or she must
do so on the basis of the principles set out in Schedule 1 of the
Regulations, which are:
1. avoiding risks;
2. evaluating the risks which cannot be
avoided;
3. combating risks at source;
4. adapting the work to the individual,
especially as regards the design of workplaces, the choice of work
equipment and production methods, with a view, in particular, to
alleviating monotonous work and work at a predetermined work rate
and to reducing their effect on health;
5. adapting to technical progress;
6. replacing the dangerous by non-dangerous or
less dangerous;
7. developing a coherent overall prevention
policy which covers technology, organisation of work, working
conditions, social relationships and the influence of factors
relating to the working environment;
8. giving collective protection measures
priority over individual protective measures; and
9. giving appropriate instructions to
employees.
Hierarchy 6: BS OHSAS 18001
BS OHSAS 18001 requires that:
...consideration shall be given to reducing the risks according
to the following hierarchy:
1. elimination;
2. substitution;
3. engineering controls;
4. signage/warnings and/or administrative
controls;
5. personal protective equipment.
In practice, it is not really important which hierarchy is used
in selecting a risk control measure or combination of measures.
What is important is that you recognise that some types of risk
control measure are more effective in the long term than others,
and that you take this into account when deciding which measures to
recommend.
Read more
How to order
To order your books: