General principles of control
6.3 The hierarchy of risk control measures
The principles of control outlined above provide a basis from which to consider the adequacy of existing control measures, both those already in place and those that are likely to be required. The principles themselves do not provide a hierarchy from which to assist confi rma-tion that the risks have been reduced so far as is reason-ably practicable, neither do they establish a hierarchy of which control or series of controls to use.
The following is a summary of the preferred hierarchy of risk control principles as outlined in the HSE publica-tion HSG65 as they relate to general health and safety.
Eliminate risk by substituting the dangerous for the less dangerous, e.g.:
➤ Use less hazardous substances
➤ Substitute a type of machine that has a better guarding system to make the same product
➤ Avoid the use of certain processes entirely perhaps by contracting out.
Combat risks at source by engineering controls and giving collective protective measures priority, e.g.:
➤ Separate the operator from the risk of exposure to a hazardous substance by fully enclosing the process
➤ Protect the dangerous parts of a machine by guarding
➤ Design process machinery and work activities to minimise the release, or to suppress or contain, air-borne hazards (LEV)
➤ Design machinery to be operated remotely and to which materials are fed automatically, thus separat-ing the operator from danger areas such as movseparat-ing blades, etc.
Minimise risk by:
➤ Designing suitable systems of working
➤ Using personal protective clothing and equipment;
this should only be used as a last resort.
HSG65’s hierarchy refl ects that risk elimination and the use of physical engineering controls and safeguards to control risk can be more reliably managed rather than
those that rely solely on people, particularly when they are prone to error.
The hierarchy shown above relates to the management of occupational safety and health issues, the hier -archy is very often extended slightly following a very similar layout enabling the effective management of both the primary and secondary fi re hazards to be considered.
The hierarchy is shown below:
Elimination EliminationElimination Substitution SubstitutionSubstitution Reduction ReductionReduction Isolation IsolationIsolation Control ControlControl
Personal protective equipment Personal protective equipmentPersonal protective equipment Discipline (personal, signage, etc.) Discipline (personal, signage, etc.)Discipline (personal, signage, etc.)
Figure 6.2 The hierarchy of risk control measures 6.3.1 Elimination
The most effective way of managing risk – removing an entire process, task or activity eliminates the risk entirely.
Perhaps changing a process that requires heat via a naked fl ame to a cold process may be possible given the technological advancement made over recent years. With regard to fi re risk management elimination can only effect-ively be used to manage primary fi re hazards although if it can be used effectively it will have an impact on man-aging the secondary fi re hazards. On many occasions it is not possible to stop undertaking a process and thus an alternative control measure or selection of control measures from within the hierarchy must be considered.
6.3.2 Substitution
The replacement of a high risk hazard, such as a solvent-based paint, with that of a risk-free or low risk alternative such as a water-based paint. A further example would be the use of battery powered hand tools as a substitute for 220/240 volt electrical tools which possess greater fi re risks not to mention slip/trip risks from the cables.
6.3.3 Reduction
Reducing can take a number of forms such as the reduction in the numbers of persons exposed to the
hazard. For example, changing the work pattern by undertaking the refurbishment of a main staircase in a busy offi ce building concourse could be undertaken out of normal working hours thereby reducing the numbers of people exposed to the work or who may be affected by the work (means of escape partially obstructed). In relation to the management of dangerous substances in the event of a fi re, a mitigating measure would be the reduction of the number of persons potentially exposed by undertaking the work in a remote or segregated area.
When considering a method of work it may be possible to apply a different technique to reduce the risks such as using a roller to apply a coating material rather that using a spray technique which may present an additional explosion risk due to the atomised spray and the presence of ignition sources.
Reduction may also be achieved by the reduction of exposure time to a hazard, such as would be the case when managing the exposure time of persons involved in the transportation, storage, use and disposal of chemicals such as solvents. The Workplace Exposure Limit (WEL) assigned to acetone, for example, is 500 ppm in an 8-hour period, thus reducing exposure to the prescribed limit ensures that persons are kept free from ill health arising from the hazardous chemical. Acetone is, however, a chemical with a low fl ashpoint so even a small amount could present a fi re and explosion risk and thus reducing the volume is also a fi re control measure.
The single biggest reduction measure in relation to dangerous substances is to reduce the quantity or amount of the substance transported, stored, handled, etc. to the absolute minimum. This could be achieved by establishing a ‘call-off’ system whereby minimum stock levels are supported by regular deliveries keeping the stock levels down to the absolute minimum.
6.3.4 Isolation
Isolating the hazard from people by enclosing the haz-ard should also be considered when elimination, substi-tution or reduction cannot be achieved. Isolation can be achieved, when handling fl ammable and reactive mater-ials, by the provision of a glovebox enclosure to prevent ill-health effects from inhaling the vapours, in addition to preventing the fl ammable vapours fi nding an ignition source causing a fi re or explosion.
Isolation of electrical supplies throughout a building (service risers) can be achieved by ensuring that the risers are fi re resistant enclosures, thus should a fi re start the secondary hazard (such as the production of smoke) is contained within the enclosure and will not have an adverse effect upon those escaping.
It may also be possible to undertake hot work within an enclosure which is fi re retardant and/or fi re resistant,
thus isolating the risk of fi re progressing outside the enclosure by containing it within.
6.3.5 Control
Control can be achieved in two separate ways, although like many of the controls discussed in this chapter they may well be used together in an overall control strategy.
Engineering controls – the use of a guard or an interlocking system is an effective engineering control for preventing access to dangerous moving parts on machinery. Engineering controls are widely used in relation to fi re safety and risk management solutions, for example smoke extract systems manage smoke levels to allow greater time to escape from large buildings and premises such as shopping centres. Sprinkler and other types of fi xed fi re fi ghting installations are installed to manage and suppress a fi re. Detection and alarm systems are engineering controls that provide early warning and a communications system in the event of a fi re (Chapter 9).
Safe systems of work (SSOW) – these are formal written procedures that describe how a process or activity is to be undertaken. The HSWA requires the production of SSOWs and that all employees know them.
There is a wide range of terminology used across industry to describe an SSOW. In the construction industry, for example, the term ‘method statement’ is used, in many production-based organisations the SSOWs are referred to as safe operating or standard operating procedures.
Regardless of the terminology used and the way they are recorded, SSOWs tend to include very similar items, such as a description of the work, its sequence, the risks and controls, etc.; further details on SSOWs are discussed later in this chapter.
6.3.6 Personal protective equipment (PPE)
Personal protective equipment should only be issued as a last resort, where risks cannot be controlled by more positive means, i.e. with controls further up the hierarchy.
Where it is issued the employer is not allowed to make any charge for its provision. The equipment must be read-ily available and employees must have clear information on how to obtain it, use it, maintain it and store it. In order to ensure the proper level of protection and comfort the PPE must be available in a range of sizes to suit the entire workforce. PPE must conform to the relevant standards and carry the CE mark.
Any PPE supplied must be suitable for the operating conditions and it must protect against the specifi c risk present. This will require the employer or responsible person to carry out an assessment of the precise need for protection and specify PPE which will meet those
General principles of control
needs. This assessment must also take into consider-ation the needs of the wearer in terms of fi t and usability.
Any PPE issued must have a supporting system to ensure it is properly maintained or replaced as necessary. The level of maintenance support required will depend on the nature of the equipment and may range from simple cleaning to a planned inspection and maintenance programme.
While PPE is seen as a last resort, there are a number of benefi ts to its use these are:
➤ It supports and enhances other control measures such as SSOWs and permit to work systems (con-fi ned space entry)
➤ It provides a solution to risk reduction where other controls are impracticable such as wearing bump caps in low head height plant room areas
➤ It can be used as an immediate interim measure to allow work to continue prior to establishing further controls such as guarding, enclosure, etc.
➤ It will be required as part of the emergency response arrangements for effectively rescuing a person from areas such as confi ned spaces or enabling isolation of power sources, service supplies, etc. in the event of an emergency.
There are a number of limitations attached to the use of PPE, the majority of which revolve around the fact that if the PPE is not worn, is damaged, does not fi t or is not maintained it will not only offer limited or no protection, it can also lead the wearer to believe that they are pro-tected even if they are not.
6.3.7 Discipline
The use of signage markings and personal discipline is the fi nal control measure covered by ERICPD hierarchy.
The reliance upon individuals following the sign’s direc-tion is immense; it is also well known that an overpro-vision of signage actually results in a person becoming
‘sign blind’ where they cannot identify what the specifi c signage denotes and will therefore not take the appro-priate course of action – this will be discussed further in Chapter 10. All signs must display a pictogram to iden-tify their meaning which may, if necessary, be supported by suitable wording.
Mandatory signs
Signs prescribing specifi c behaviour Circular sign
Blue ground (50% of area of sign) White border and pictogram.
E.g. fi re door keep shut.
Prohibition signs
Signs prohibiting behaviour likely to cause or increase danger.
Circular sign
Red edging and cross stripe (35% of area) White ground
Black pictogram.
E.g. No smoking.
Warning signs
Signs giving warning of a hazard or danger.
Triangular sign
Yellow ground (50% of area) Black edging and pictogram.
E.g. Explosive atmosphere.
Emergency escape or fi rst aid signs
Fire safety signs (also known as safe condition signs).
Signs giving information on emergency exits, fi rst aid, res-cue facilities, etc.
Rectangular or square sign Green ground (50% of area) White pictogram.
E.g. Emergency exit.
Figure 6.4 A typical no smoking sign Figure 6.3 Typical fi re door keep shut sign
Fire signs
Signs showing the direction to, or location of, fi re fi ght-ing equipment.
Rectangular or square sign Red ground (50% of area) White pictogram.
E.g. fi re extinguisher.
an organisation will directly affect each of the elements of the hierarchy of controls if elimination has not been achieved. Therefore discipline in the shape of supervision and monitoring will also form part of the control process.
It is likely that rather that placing reliance upon any one individual control measure covered in ERICPD a combination of controls outlined in the hierarchy will often be required and then supported by an appropriate level of supervision and monitoring.