Hierarchy of prevention and control measures

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Klaus Kuhl (Kooperationsstelle Hamburg IFE GmbH), Carsten Brück (Kooperationsstelle Hamburg IFE GmbH)


Employers need to assess the risks for their staff, and then preventive measures or control measures have to be derived from this assessment. The types of measures can be classified as: elimination of the hazards (e.g. designing new work processes) and, if that is not possible, minimising and separating the hazards from the workers by

i) technical measures (e.g. encasing, exhaust),
ii) organisational measures (e.g. only qualified employees are allowed to do specified work),
iii) personal measures (e.g. wearing PPE),
iv) behavioural measures (e.g. peer-observation).

Legislation requires following the hierarchy in order to always select the most effective type of measure.

What is understood by the hierarchy of prevention and control measures?

Risks may cause suffering to people, losses for companies and damage to our economy, and, as such, they should be avoided or – where this is not possible – reduced to a minimum. Common sense and legislation dictate that employers assess the risks for their staff and implement related preventive or control measures. Preventive measures aim at avoiding risks whereas control measures are put in place in order to reduce and manage risks.

To combat the vast number of very different risks, for example slipping, falling, developing musculoskeletal disorders (MSD), radiation, stress, etc., researchers, technicians and practitioners have developed an even higher number of preventive and control measures. This means that employers need guidance in order to choose the most efficient measure. To facilitate this, measures are classified, e.g. as elimination measures, technical measures, organisational measures or personal measures, and these types are put into a hierarchical order. The highest level is seen as the most efficient one in terms of combating the risks. The lower levels are only to be applied, if no higher level measures are available, or if the application would be disproportionate in terms of effort and achievable result. In most cases, a package of measures should be applied, whereby the individual measures could be attributed to different hierarchical levels.

The importance of following the hierarchy

The importance of following a hierarchy becomes clear when looking at the following example, adapted from Stewart [1]. A noisy machine is encased and insulated (technical measure). Otherwise the workers in the workshop would have to wear ear protection. However, not all workers always wear the protection, some ear protective equipment may not fit correctly, and others may not be worn in the stipulated manner. This will render the personal measures less efficient as compared to the technical measures. Nevertheless, technical measures also have their shortcomings. They may not be efficient enough as to allow workers to go about their work unprotected. They may be manipulated because workers regard them as interrupting their work process in an unacceptable way, or as too time consuming. Maintenance workers may have to do their job inside the encasing while the machine is running. Therefore, the best measure would always be to avoid or eliminate the hazard altogether.

Different hierarchies, legal requirements

Different hierarchies of prevention and control measures have been developed by different institutions. For an overview see e.g. Boyle [2]. The BS OHSAS 18001 hierarchy can be seen as a typical system, as presented by Boyle:

  1. Elimination;
  2. Substitution;
  3. Engineering controls;
  4. Signage/warnings and/or administrative controls;
  5. Personal protective equipment.

The different systems have their advantages and their shortcomings; however, stakeholders should be aware of the legal requirements. These are in the first instance laid down in the EU ‘OSH Framework’ Directive 89/391 (see also: Legislation), adopted in 1989 as ‘general principles of prevention’ [3]:

(a) avoiding risks;
(b) evaluating the risks which cannot be avoided:
(c) combating the risks at source;
(d) adapting the work to the individual, especially as regards the design of work places, the choice of work equipment and the choice of working 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.
(e) adapting to technical progress;
(f) replacing the dangerous by the non-dangerous or the less dangerous;
(g) developing a coherent overall prevention policy which covers technology, organization of work, working conditions, social relationships and the influence of factors related to the working environment;
(h) giving collective protective measures priority over individual protective measures;
(i) giving appropriate instructions to the workers.

In other places, the Directive further explains the training needs and demands that ‘workers receive health surveillance appropriate to the health and safety risks they incur at work’.

The first system looks straightforward at first glance, however, it raises a common problem, namely that employers often see no possibility for elimination or substitution. Engineering measures are put in place (or even sometimes just personal measures) and little effort is put into reducing the hazards [4].

The second system cannot serve as an easy tool for an employer at a small company as it would need some interpretation or closer scrutiny.

The Directive has, however, two clearly distinguishable hierarchical levels:

  1. Avoid the risks or eliminate the hazard
  2. Reduce the hazards and the risks

This means that an employer must not limit the control measures to e.g. encasing a noisy machine, but has to ‘combat the risk at source’ i.e. consider improving the machine, buying a new, less noisy machine, or searching for a different process that will reduce the emission altogether. ‘Adapting to technical progress’ is a continuous task.

The second step ‘Reduce the hazards and the risks’ has two implications, which are strongly interlinked, and this is unfortunately not really apparent in the first hierarchical system:

  • If it is not possible to avoid the risks or eliminate the hazards, then the next step has to be to reduce/minimise the hazards AND separate the remaining hazards from the workers [5].

Thereby, for both strategies – reduction and separation – technical, organisational and personal measures can be employed, and ‘collective protective measures’ should be given ‘priority over individual protective measures’.

As has been indicated in the example in the second chapter, the manipulation of engineering controls is not uncommon: The German Social Accident Insurance DGUV established that approx. 37% of all safety appliances for metal processing machines in Germany are bypassed [6]. In most cases, the reason is the time factor, i.e. workers feel disrupted in their work process or they feel under time pressure [6]. Subsequently, the behaviour of workers has come into focus, and some institutions have complemented hierarchical systems by a further level of ‘behavioural oriented measures’ [7] , i.e. measures that aim to improve the safe behaviour of workers. These measures include such methods as peer-observation and peer-discussion and need preconditions, such as establishing a no-blame culture among managers and supervisors, and valuing proposals by diligent feed-back [8].

Finally, all these measures need ‘appropriate instructions’ and training, as well as possibly health surveillance, where risks cannot be avoided.

Based on the discussion above, the full hierarchical system including some guidance would look as follows:

Table 1: Hierarchy of control measures and guideline

Hierarchy of control measures
Avoid risks, eliminate hazards

Reduce, minimise hazards
separate hazards from persons (workers, visitors, etc.)

… by technical measures
… by organisational measures
… by personal measures
Improve safe behaviour
Guidance to hierarchy
Training and instructions to be provided at all levels

Health surveillance may be needed where risks cannot be avoided.

Adapt to technical progress, i.e. re-check frequently.
Before applying measures at a lower level, the possibility of applying measures of a higher level has to be thoroughly investigated.

In difficult cases, this may need specialists’ knowledge; data bases, external experts, labour inspectors etc.
In most cases, a package of measures should be applied, whereby the specific measures may be attributed to different hierarchical levels.

Source: Adapted from South Australian Unions [5] and Rundnagel [7].

Efficacy of control measures

Boyle discusses the question of how to select the best option of prevention and control measures and presents some criteria [2]:

  • 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.

The author concludes: ‘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’ [2].

In 2009, the benOSH study (benefits of occupational safety and health) established the costs of work related accidents and diseases and compared these with the costs of optimum prevention measures that could have prevented or reduced the incidents [9]. The study concluded: ‘The highest values can be found for measures aimed at substitution or avoidance. The lowest values can be found for measures such as training and personal protective equipment. These results seem to support the case that measures considered to be the most effective according to the prevention principles are also more cost-effective (profitable)’. [9]

Different studies have used the hierarchy to classify the preventive measures, for example Transport Research Laboratory [10].

The question of why companies would rather implement technical and personal measures but leave out efforts to eliminate or reduce hazards was studied by Ahrens et al. [4]. The authors concluded that efforts by companies meet a number of challenges:

  • Attitude: never change a running process, as process changes may bring about uncertainties
  • No priority neither at enterprises nor in practical governance
  • Dealing with the current problems is already too laborious; no additional problems by an unnecessary innovative approach (existing standards etc.)
  • Uncertainty in risk assessment – a shift of risks may be possible
  • Substitutes are less tested in practice
  • Integration in the production chain makes an innovation beyond enterprise borders necessary
  • Technological or economic difficulties

The authors have identified influential factors, such as society, public policy, regulation, market forces, etc. that all have to play a role in order to overcome these difficulties. See also: The hierarchy of control measures applied to dangerous substances.

The difficulties in applying the hierarchy of control measures in practice have caused the European Agency for Safety and Health at Work, EU-OSHA, to provide good practice examples on how to eliminate or combat risks at source [11]. The cases cover different sectors, such as: roadwork, office work, metal sector, railway, health sector, mines, packaging and cement production. A similarly wide range of issues was presented, namely: ergonomics, accident prevention, chemicals, biological risks, psychosocial problems, noise, electricity and climate. The authors present success factors, amongst others:

  • Support from top management. This is essential to ensure that necessary resources such as budget, human resources, equipment, etc., are made available for the project.
  • Involvement of relevant actors such as workers themselves (participatory risk assessment), human resources, financial department, OSH practitioners, etc. An important group that has to be motivated and involved from the beginning are the workers. They should be involved not only in the risk analysis itself but also during the identification and implementation of possible solutions. Their practical and detailed knowledge and competence is often needed to develop workable preventive measures.
  • A good analysis/knowledge of effective potential solutions, best practice and scientific or technological innovations available.

Examples for systems, machines, equipment, radiation, substances and psychosocial risks

The following table gives some examples of possible measures for all levels of the hierarchy and for different types of risks:

Table 2: Examples of prevention and control measures per hierarchy levels

Hierarchy levels Prevention and control measures
System Machine Equipment Substance Radiation Psychosocial risks
E.g. windows in buildings E.g. guillotine E.g. ladder E.g. halogenated solvents E.g. noise from punch E.g. negative stress
Avoid, eliminate hazards Windows open inside, no leaning out for cleaning No cutting of sheets needed due to new product design Maintenance control box put down to floor level. Cleaning by vibration, substitution with non hazardous substances Laser cutting instead of punching Beneficial social climate, optimal work organisation
Reduce, minimise hazards

separate hazards from persons (workers, visitors, etc.)

by: technical measures a) use specially coated glass
b) use moveable elevating platform
a) less cutting, new machine
b) guards, encasings
a) move-able scaffold
b) safety ladder
a) substitute with less hazardous substances
b) encasing, exhaust
a) new punching machine
b) encasing
a) optimal equipment
b) optimal lay-out of rooms
organisational measures a) only qualified specialists allowed to do the work
b) health monitoring
a) only qualified specialists allowed to operate machine
b) health monitoring
a) only qualified specialists allowed to use equipment
b) health monitoring
a) only qualified specialists allowed to use substances
b) health monitoring
a) only qualified specialists allowed to work in area
b) health monitoring
a) participation in work organisation
b) health monitoring
personal measures Harness Gloves, goggles Shoes, harness Mask Ear protection Anti-stress training
Improve safe behaviour E.g. peer observation; preconditions: example-setting by managers and supervisors, no-blame culture, feed-back.

Source: Examples summarised by K. Kuhl [12].

The examples illustrate that technical and organisational measures are usually twofold: aiming at a reduction of the hazards and aiming at separating hazards and persons. Personal measures can also be used to reduce hazards by e.g. selecting qualified personnel for specific tasks, who use less chemicals etc. The examples also illustrate, that instruction and training are needed for almost all of the measures. Elimination measures, technical, organisational, personal and behavioural measures all need to be explained, discussed, tested and practiced.

Methods and tools to select control measures

An important method for selecting the control measure is to involve the workers who are actually affected by the task into the risk assessment, the selection of measures and the testing of these. In its campaign booklet EU-OSHA notes: ‘Workers and their representatives have the detailed knowledge and experience of how the job is done and how it affects them. For this reason, workplaces in which workers actively contribute to health and safety often have a lower occupational risk level and accident rates’ [13].

There are also tools available to support employers, managers, OSH professionals, safety representatives and affected workers in conducting risk assessments and in selecting the most appropriate measures. A Europe wide online interactive tool for risk assessment called OiRA (Online interactive Risk Assessment) is being established by EU-OSHA [14]. OiRA is a comprehensive, easy to use and cost-free web application. It helps micro and small organisations to establish a thorough step-by-step risk assessment process – from the identification and evaluation of workplace risks, through decision making on preventive actions and the completion of these actions, to continued monitoring and reporting. Users are guided through the identification of measures whereby the hierarchy of measures is applied semi-automatically.

The British Health and Safety Executive, HSE, present several online risk assessment tools [15] and the German Federal Institute for Occupational Safety and Health, BAuA, has established a separate website for risk assessment and the selection of appropriate measures [16].


  1. Stewart, J. ‘Occupational hygiene: control of exposures through intervention’, Encyclopaedia of Occupational Health and Safety, ILO (Ed.), 2003. Available at: http://www.ilo.org/safework_bookshelf/english/.
  2. 2.0 2.1 2.2 Boyle, T., Health and safety: risk management, IOSH Services Ltd, Leicester United Kingdom, 2008.
  3. EU – European Union, Council Directive of 12 June 1989 on the introduction of measures to encourage improvements in the safety and health of workers at work (89/391/EEC), consolidated version as per 3/2008. Available under (retrieved 15 March 2012): http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:01989L0391-20081211:EN:NOT.
  4. Ahrens, A., Braun, A., von Gleich, A., Heitmann, K., Lißner, L., Hazardous Chemicals in Products and Prozesses - Substitution and Beyond, Series: Innovation and Sustainability, Physica-Verlag, Heidelberg, Berlin, 2006.
  5. 5.0 5.1 South Australian Unions, General guide Occupational Health Safety and Welfare in South Australia, online training materials. Retrieved 15 March 2012, from: http://www.saunions.org.au/ohs/hierachy_of_controls.htm.
  6. 6.0 6.1 HVBG – Hauptverband der gewerblichen Berufsgenossenschaften, Manipulation von Schutzeinrichtungen an Maschinen, 2006. Available at: http://publikationen.dguv.de/dguv/pdf/10002/reportgesamt-manipulation.pdf.
  7. 7.0 7.1 Rundnagel, R, Grundlagen der Gefährdungsbeurteilung (basics of risk assessment), VBG, no publishing date. Retrieved 12 March 2012, from: http://www.ergo-online.de/site.aspx?url=html/gefaehrdungsbeurteilung/grundlagen_und_anforderungen/grundlage_der_gefhrdungsbertei.htm.
  8. Bördlein, C., Faktor Mensch in der Arbeitssicherheit – BBS (human factor in occupational safety – BBS), Erich Schmidt Verlag, 2009.
  9. 9.0 9.1 Van den Broek, K., De Greef, M., Van Der Heyden, S., Kuhl, K., Schmitz-Felten, E., Final Report – Socio-economic costs of accidents at work and work-related ill health, European Commission, Directorate-General for Employment, Social Affairs and Inclusion, 2011.
  10. TRL – Transport Research Laboratory, Review of workplace control measures to reduce risks arising from the movement of vehicles, prepared for the Health and Safety Executive, 2002. Available at: http://www.google.com/url?q=http://www.hse.gov.uk/research/rrpdf/rr038.pdf&sa=U&ei=oR5jT-XaEsK2hAfQ-52GCA&ved=0CAQQFjAA&client=internal-uds-cse&usg=AFQjCNGtZHZq3VIXhXPKg8dMwpFEVSJWLg.
  11. EU OSHA – European Agency for Safety and Health at Work, Assessment, elimination and substantial reduction of occupational risks, prevention report, Office for Official Publications of the European Communities, Luxembourg 2009. Available at: http://www.google.com/url?q=http://osha.europa.eu/en/publications/reports/TEWE09001ENC&sa=U&ei=IzpjT5b2BpCcOqGEqYII&ved=0CAQQFjAA&client=internal-uds-cse&usg=AFQjCNFhPGNVZFUp2fmrDk0spKkSUseo0g.
  12. Kuhl, K., Examples on hierarchy levels, Kooperationsstelle IFE, 2012, unpublished.
  13. EU-OSHA – European Agency for Safety and Health at Work, Worker Participation in Occupational Safety and Health – A Practical Guide, Bilbao 2012. Available at: http://www.healthy-workplaces.eu/en/worker-participation/worker-participation-guide#mainContent#appendix.
  14. EU-OSHA – European Agency for Safety and Health at Work, OiRA - online interactive risk assessment (no publishing date). Retrieved 16 March 2012, from: http://www.oiraproject.eu.
  15. HSE – Health and Safety Executive, Risk Management (no publishing date). Retrieved 16 March 2012, from: http://www.hse.gov.uk/risk/index.htm.
  16. BAuA - Federal Institute for Occupational Safety and Health, Risk assessment (no publishing date). Retrieved 16 March 2012, from: http://www.gefaehrdungsbeurteilung.de/en?set_language=en.

Links for further reading

ILO (Ed.), Encyclopaedia of Occupational Health and Safety, Geneva, 2003

EU OSHA – European Agency for Safety and Health at Work, Risk assessment (no publishing date). Retrieved 19 March 2012, from: http://osha.europa.eu/en/topics/riskassessment.