Maintenance is an essential function in enterprise. Maintenance is carried out in all sectors and all workplace. Working in the maintenance trade often means working during stop, start-up, shut-down, or disrupted operating phases, giving rise to potential risks in terms of accidents or exposure to many hazards. The work often requires maintenance workers to remove or dismantle collective protective equipment; as such equipment is not effective for their type of work. Maintenance workers have more serious and more frequent accidents than production workers. More so than for any other activity, maintenance-related accidents are characterised by their many different causes.
Maintenance: a wide variety of activities
Maintenance is essential to keep equipment, machines, buildings and structures (such as bridges or tunnels), as well as the work environment, safe and reliable. Maintenance work includes a variety of activities across very different sectors and types of working environments. It typically comprises servicing, repairing, inspecting, testing, adjusting or replacing parts and may involve, for example, opening closed production systems, exchanging filters, removing paint layers, blasting, grinding, sanding, applying fillers, applying paint, insulating, and repairing a power grid, gas supply or water supply.
According to the European standard EN 13306 maintenance can be defined as a "combination of all technical, administrative and managerial actions during the life cycle of an item intended to retain it in, or restore it to, a state in which it can perform the required function". It implies a differentiation between preventive maintenance and corrective maintenance (figure 1) .
Corrective maintenance is carried out after the occurrence of a failure in order to eliminate the source of the failure or to reduce its occurrence. It can be carried out immediately after the failure occurs (remedial maintenance such as emergency interventions, breakdown) or it can be delayed to limit the interference of the production process (deferred). Especially the unforeseen nature of remedial maintenance makes it a high-risk activity. Preventive maintenance is carried out at predetermined intervals to reduce the probability of failure. These maintenance activities can be part of a worker’s daily routine, for example cleaning and checking a spray gun at the end of a working day. Improvement maintenance is aimed at reducing the need of maintenance by making changes in the process or by engineering solutions.
Maintenance can be carried out in shutdown conditions (the whole production line or parts of production are stopped) or in normal working conditions. Depending on the circumstances, shutdown conditions are considered safer than maintenance during working production.
Maintenance covers a variety of occupations and it concerns all sectors of activity (buildings, machines, plants, infrastructures, roads need to be serviced, repaired and maintained more or less regularly....). For these reasons, it is difficult to identify the exact number of workers involved in maintenance activities. Data from France and Spain  indicate that about 6% of the working population is involved in maintenance tasks. The majority of maintenance workers are men (around 90% in France and 65% in Spain), and within this category of workers the largest age group is 30-49 years. Because they carry out a wide range of different activities (inspection, testing, measurement, replacement, adjustment, repair, upkeep, fault detection, replacement of parts, servicing, lubrication, cleaning), maintenance workers are exposed to many and various occupational risks.
Exposure to risk factors
Higher exposure As maintenance is carried out to some extent in all sectors and workplaces, maintenance workers are more likely than other workers to be exposed to a broad range of occupational hazards. Data from the Spanish working conditions survey  indicate a higher exposure of maintenance workers to noise, vibration and different kinds of radiation when compared to the rest of the working population. Maintenance workers are also more exposed to heat in summer (44% compared to 19% among other occupations), cold in winter (44% compared to 17%) and a humid atmosphere (25% compared to 13%), and are more exposed to dangerous substances, vapours and fumes. Maintenance workers are more likely than other employees exposed to a wide variety of risks, which may lead to various occupational diseases. There are:
- physical risks: noise, vibration, excessive heat and cold, radiation, and high physical workload, ergonomics-related risks,
- chemical risks: asbestos, glass fibre, vapours, fumes, dust, solvents, polychlorinated biphenyls (PCBs) (for maintenance workers who carried out their job in public buildings in the 60’s),
- biological risks: bacteria ex.Legionella, Leptospir, mould and fungi, and
- psychosocial risks: time pressure, shift work, stress, often related to poor work organization.
"Specific risk factors" In addition to the risks associated with any working environment, maintenance operations involve some specific risks.
Maintenance often includes working alongside a running process and in close contact with machinery. In maintenance activities, contrary to production modes, direct contact between the worker and the machine cannot always be reduced substantially as maintenance is an activity where workers need to be in close contact with processes. Maintenance often involves unusual work, non-routine tasks in abnormal operating conditions requiring the use of a-typical, unfamiliar, equipment. This increases the risks since normal operations, routine and automation typically diminish the likelihood of human error that can lead to accidents. Especially under time pressure, e.g. in case of a breakdown, an acute failure, high-priority repairs, risk control measures can be disabled, e.g. accessing a closed work area to solve a machine stoppage or ignored. Maintenance involves changing tasks and working environment. This is especially true in case of contract workers (see below 4.).
The risks are increased when working in confined spaces, which happen quite often in maintenance activities, e.g. workers maintaining ship vessels have to enter various confined spaces such as holds, tanks, compartments, cofferdams, double bottoms, bilges and galleys.
Working in confined spaces may pose workers at risk of:
- Overcome by gas, fumes, vapours or lack of oxygen
- Drowned by water or free-flowing solids
- Injured due to fire or explosion.
- Overcome by high temperature
It is essential that the risks associated with each confined space are fully assessed, and that the appropriate planning and preparation for the work is undertaken.
Data on accidents of maintenance workers
Maintenance workers are also at risk for all types of accidents accidents. Analyses of EUROSTAT data based on the ESAW (European Statistics on Accidents at Work) methodology can help identify accidents related to maintenance operations in several European countries. Within the variable ‘working process’, used for classifying causes and circumstances of accidents, there are four ESAW subcategories that are related to maintenance operations:
- setting up, preparation, installation, mounting, disassembling, dismantling;
- maintenance, repair, tuning, adjustment;
- mechanised or manual cleaning of working areas and machines;
- monitoring, inspection of manufacturing procedures, working areas, means of transport, equipment – with or without monitoring equipment.
The number of accidents related to these subcategories was compared with the total number of accidents related to any other subcategory within the variable 'working processes'. The data show that around 20% of all accidents in Belgium (in 2013) were related to maintenance operations, as well as around 18-19% in Finland, 14-17% in Spain, and 10-14% in Italy (in 2003-2006). Additionally, the figures from several European countries indicate that in 2006 around 10-15% of all fatal accidents were related to maintenance operations .
EUROSTAT data from five EU countries indicate that the majority of maintenance-related accidents occur in manufacturing, construction, real estate, renting and business activities, and, in Austria, also in hotels and restaurants. Maintenance workers in the electricity, gas and water supply sector were also at increased risk of accidents. E.g data for Finland show that 50% of all accidents in this sector were related to maintenance activities. But also maintenance activities in the real estate and business sector and the education sector show an increased amount of accidents compared with other sectors (15-20%). In France, 14% of fatal accidents are related to maintenance of machines, devices and equipment. This percentage rises to 44%, if so-called “large scale/heavy" maintenance (retrofits, improvements, etc.) activities are taken into account . Moreover, an AFIM study emphasises that mortality occurrence in maintenance activities is five times higher than the average mortality occurrence for all occupational activities combined .
Scientific studies indicate that occupational diseases and work-related health problems are also more prevalent among workers involved in maintenance activities. A study by AFIM (French association of maintenance engineers) on a population of maintenance workers shows an occupational disease rate 10 times higher than for other workers, mainly related to exposure to asbestos, benzene and noise .
However, as emphasised by Reason & Hobbs , maintenance activities receive little attention and few prevention studies have been dedicated to these activities . It is still difficult to know the number of maintenance workers and to identify them in surveys or in the statistics of occupational accidents and diseases. Moreover, most of the studies concerning this subject are focused on risks related to the maintenance environment and to the equipment concerned (physical, biological, chemical, and other risks, and hazards) or to risks related to isolation and energy dissipation and restarting. Few studies have been aimed at investigating the relations between maintenance organisations and safety.
Maintenance as a risk factor influencing accidents and illnesses
According to Blaise, out of 93 accidents studied, 27% were linked to a risk unforeseen by the victim. Some maintenance activities are performed on equipment, without being cut off from its energy sources. 76% of accidents resulted from intervening either on a continuously operating machine or from machine restart. Finally, it should be stressed that, out of these 93 accidents, 41% were related to a lack of normal protection, i.e. protective devices imposed by regulations or state of the art. Little data are available for determining which maintenance operations feature the greatest risks. Nevertheless, it seems that the repair phase poses the greatest risk with 46% of maintenance related accidents, followed by the troubleshooting phase with 26% of maintenance-related accidents. However, the dangerous nature of cleaning, machine setting, lubricating, and other tasks is also highlighted.
The organisational approaches consider that risks also have root causes in maintenance work  and in the system at large. The origins of unsafe events could be traced back to latent conditions within the "normal" carrying-out of maintenance work and within the maintenance work organisation and policy. Hence, an accident sequence may begin with the maintenance policy. The latent conditions for dysfunction that are created are transmitted along the organisational pathways to the real conditions for carrying out the maintenance work. Evidence suggests that maintenance related activities could be linked to the causes of several major accidents. Especially in the chemical process industry accidents investigations came to the conclusion that deficiencies in maintenance management played an important role in major accidents 
Maintenance activities are critical for the health and safety of maintenance staff; they may also be critical for others, in particular, for the equipment users or the production operators. The relationships between maintenance and production explain that:
- some accidents may be related to maintenance failings, i.e. insufficient, inappropriate or late maintenance; for example, if maintenance is not carried out with sufficient frequency, the equipment or the installation may become dangerous for maintenance and for production staff;
- other accidents may result from the co-activity of the two types of operators (repair without interrupting operation, for example).
Two major aspects are responsible for maintenance being a high risk activity: technical and organisational developments. The nature of maintenance is changing with the increasing complexity of industrial machinery: it is undergoing a genuine transformation due to the equipment to be maintained being increasingly complex ("mechatronics" – the intervention is no longer only on the mechanics, it is also on the electronics...). And, whereas traditionally, maintenance used to be performed by an independent and centralised department or unit with specialist operators, it is now organised differently and takes many different forms: subcontracting, transfer of servicing tasks to users, geographically organised maintenance, more versatile (less specialised) maintenance operators, etc. These organisation choices may have major consequences for safety.
Safety for production process equipment is relatively well addressed by the regulatory and normative guidelines. Working equipment manufacturers have been applying these guidelines. In contrast, other activities and work processes such as adjustment and maintenance-related processes are as yet relatively poorly integrated because they are not so well studied regarding safety. And yet, more than for other activities, prevention in maintenance is highly related to risk elimination at the design stage, rather than substitution (most often related to the process), or collective or individual control measures. And yet maintenance operations remain necessary; it is impossible to guarantee that machinery will not suffer degradation or indeed failure, and machinery also simply needs to be serviced. Specific regulatory requirements exist, as do normative specifications. However, it is necessary to emphasise their existence to help designers take them on board. The characteristics of the equipment to be maintained prove to be a decisive factor in performing the intervention safely. The characteristics of the building where the equipment has to be installed are also very important. For example, the permanent easy access to machinery must be ensured. Buildings and structures that are not maintained regularly eventually become unsafe not only for the people who work in them, but also for those who enter them and even pass by them. One of the best ways to prevent and control occupational risks related to maintenance is to address them early in the design process of buildings and structures, work environments, materials, and plant (machinery and equipment). Also for buildings and structures it is important to consider for example repair work at the façade already at the design stage, so to avoid risky operations.
Prevention through design: eliminating hazards at the design stage
Preventive measures for maintenance operations have to start at the design stage. Preventive design is key for machines, buildings, structures, infrastructures, cars, road and vessels. One of the best ways to prevent and control occupational risks related to maintenance is to address them early in the design process of buildings and structures, work environments, materials, and plant (machinery and equipment).
Safety and health hazards are often created by poor workplace design; this could be the case for example for the design of workplaces where the maintenance of airplanes and of trains takes place. Including analysis of specific requirements of tasks that would be performed in the building prevents a number of hazards from being “built in" to new workshops, eliminating, for example, some of the ergonomic risk factors involved by making sure that sufficient space is allotted to specific tasks. Other issues that can be considered at this stage are guaranteeing safe access to work areas, or separating particularly noisy procedures from the general workshop to limit workers’exposure to noise. Involving maintenance workers already at this stage will help indentify critical issues.
Planning can begin even with the design of work equipment, and by making sure that the necessary information for its safe maintenance is provided by the supplier or manufacturer of equipment. Organisations should have procurement procedures in place, to ensure that they have the necessary tools and personal protective equipment to carry out safe maintenance. For example, temporary lighting may need to be explosion-protected, or respirators may need to be provided when cleaning filters.
When new machinery or buildings are being procured, organisations should consider the ease of access that they allow for carrying out maintenance.
Considering future maintenance issues while the machine is being designed helps eliminate hazards and minimise the potential of injury while the machine is being serviced or repaired. The Council Directive 2006/42/EC on machinery lays down the essential health and safety requirements in relation to design and manufacture in order to improve the safety of machinery placed on the market. Machinery must be designed and constructed so that it is fit for purpose, and can be operated, adjusted and maintained without putting people at risk, when such operations are carried out. Firstly, machinery must be designed in such a way that the need for operator intervention is limited. So, adjustment and maintenance points must be located outside danger zones. It must be possible to carry out adjustment, maintenance, repair, cleaning and servicing operations while machinery is at a standstill. If this is not possible for technical reasons, measures must be taken to ensure that such operations can be carried out safely. Machinery must be fitted with means for isolating it from all energy sources. Many accidents or exposures are due to interventions on continuously operating machinery, or while machinery is being restarted. Could those accidents have been avoided if the machinery had been deprived of its energy sources, i.e. subjected to isolation and energy dissipation? And was such isolation and energy dissipation possible? Certain types of intervention (troubleshooting, testing, adjustment, etc.) need to be performed with energy being supplied. Very often, isolation and energy dissipation is presented as a panacea for which there is no alternative. In addition, machinery manufacturers’ instruction handbooks recommend isolation and energy dissipation for any maintenance intervention, without taking account of the real intervention conditions and of the needs of such intervention.
Paragraph 1.6.2. of Directive 2006/42/EC, relating to access to operating positions and servicing points, stipulates that “Machinery must be designed and constructed in such a way as to allow access in safety to all areas where intervention is necessary during operation, adjustment and maintenance of the machinery." Naturally, this requirement consists in providing access means in order to make the operating positions safe from risks of falls, and in order to reinforce the ergonomics of them, operating positions remaining a crucial point in the working conditions of maintenance operators. It should, however, be pointed out that making applies to all risks, be they mechanical, physical, chemical, etc.
Limits of a point of view strictly based on design
Naturally, these requirements remain very general. However, applying them is not always easy and requires a non-negligible amount of thinking from the designer. Another difficulty relates to making measures taken for one mode compatible with another mode. Hazards can differ depending on the mode of intervention; for the same hazard, the protective means can also differ depending on the mode. Finally, one means of protection for one operating mode can be a source of harm or damage for another mode. Optimising the prevention solutions is therefore not easy and it is by risk analysis that we can organise prevention measures hierarchically. “Safe maintenance" of equipment is strongly related to a promising integration of health and safety aspects in the design phase. Manufacturers and maintenance experts need to cooperate in this early stage in order to avoid risks in the use of the machines. Good machine design is necessary but not sufficient to guarantee the health and safety of users. The employer must also see to organisational measures and training of its staff.
Use of subcontracting for maintenance operations has grown considerably in recent decades. Maintenance is one of the most subcontracted functions in industry.This applies to large process industries (oil-refining, chemicals, steel, etc.) that wish to refocus on their core trades, but also to smaller industrial structures and to tertiary structures (maintenance in office buildings for example). Subcontracting maintenance is often considered an aggravating factor in terms of the safety and health. The maintenance workers have to adapt to very different working environments due to frequent changes of workplaces and it increases the road-related risks due to frequent travels. Subcontracting of maintenance can also lead many subcontracting companies to operate simultaneously on sites where the conditions in terms of work organisation and time pressure are different and determined by the user company.
The determination of the right duration attributed to each maintenance operation could be an additional risk factor. The shut-down time is expensive for the user firm which tends to reduce it. Too short a time for performing the work can lead to poor organisation, increasing the risk of accident or of exposure to chemical pollutants. In the same way, low market prices due to exacerbated competition between contractors do not allow the contracting firm to perform the work under good conditions, with consequences in terms of occupational health and safety.
Studies on health at work for sub-contracting employees are few, but they unanimously show that their working conditions (organisation of hours and work, quality of work tools, etc.) are not as good on the whole as for employees who work in-house. Indeed, the tasks they are assigned tend to be more dangerous, which reveals a trend whereby the user company out sources risk to the external company.
The STED epidemiological survey (EDF-DATR sub-contracting) conducted in 1993 on a cross-section of 2,500 DATR employees emphasises the consequences of sub-contracting in nuclear maintenance activities on the health of employees. For instance, it highlights the fact that in terms of exposure to ionising radiation, sub-contracting employees absorb 85% of the annual radiological dose, comparatively to EDF workers who only absorb 15%. But it also shows that the health risks are increasing due to the fact that these sub-contracting employees who intervene in facilities only from time to time are unable to manage their work environment like the permanent employees.
Generally, there are different types of strains for these sub-contracting employees:
- Time pressure due to the high daily amplitude of working hours, but also to the absence of weekly rest.
- Pace of work strains due to emergencies, interruptions, waiting time, etc.
- Physical work load,
- Environmental hardness due to noise, heat and exposure to toxic substances.
- Mobility constraints shown by the fact that a quarter of the employees asked are absent from home more than six months of the year.
In terms of occupational risk prevention, this organisational choice is not neutral. Risk assessment remaining the starting point for any occupational safety and health policy, the context is not the same when maintenance is done in-house as when the rationale is to have it done by contractors.
Maintenance carried out by a contractor must be well integrated into the ongoing activities of the company to safeguard the safety and health of all workers involved. Good practice examples where the needs of both the contractor and Host Company are taken into consideration include ‘good neighbour schemes’, ‘safety passports’ and induction procedures. During the whole process good maintenance management should ensure that maintenance is coordinated, scheduled and performed correctly as planned, and that the equipment or workplace is left in a safe condition for continued operation.
"Good neighbour schemes" should include the conditions under which contractors are received (dedicated areas, cloakrooms, toilet and washroom facilities, etc.), information and training specific to the structure of the site (plan, access and utilities, alarm and evacuation procedures, etc.) and to its particular risks. Specific co-operation between the occupational safety and health structures of the various firms may also be organised: exposure (atmospheric or biological) may be monitored by the user firm, more used to managing any pollutants present on its site.
A good practice: a continuously updated prevention plan.
In France for example, the workers from the contractor are not directly subordinate to the user firm’s maintenance department. The company manager of the contractor retains all of his prerogatives. A prevention plan is mandatory under all circumstances. Its aim is to organise, under the responsibility of the user company’s manager, the prevention of risks related to interference between the various firms as regards staff, equipment, or processes. The plan is based upon a joint risk assessment, also involving the occupational physicians and the institutions representing the staff and should adapt continuously so as to adopt the working method and the prevention measures most appropriate for each operation.
 CEN EN – European Committee for Standardisation. EN 13306:2010 Maintenance - Maintenance terminology. Retrieved 24 February 2015, from: http://standards.cen.eu/dyn/www/f?p=204:110:0::::FSP_PROJECT,FSP_ORG_ID:30889,6300&cs=185D3D279BC825A8A37CCE9A570701B9D
 EU-OSHA – European Agency for Safety and Health at Work, ''Maintenance and OSH — A statistical picture'', 2010. Available at https://osha.europa.eu/en/publications/literature_reviews/maintenance_OSH_statistics/view
 Instituto Nacional de Seguridad e Higiene en el Trabajo, VI Encuesta nacional de condiciones de trabajo, Madrid, INSHT, 2007. Available at: http://www.oect.es/Observatorio/Contenidos/InformesPropios/Desarrollados/Ficheros/Informe_VI_ENCT.pdf
 FAO – Fonds voor arbeidsongevallen. ''Verdeling van de arbeidsongevallen volgens het soort werk en de gevolgen van het ongeval – 2013''.
 Grusenmeyer, C., ''Les accidents liés à la maintenance. Importance et caractérisation: étude bibliographique'', Cahier de Notes Documentaires, Hygiène et Sécurité du Travail, N° 201, 2005, pp. 31-44. http://www.inrs.fr/inrs/recherche/etudes-publications-communications/doc/publication.html?refINRS=A.8%2F1.012%2F4314%2FNS%20248
 AFIM – Association française des ingénieurs et responsables de maintenance - ''Guide national de la maintenance'', Association française des ingénieurs et responsables maintenance, Paris, 2004, pp. 37-66
 Reason, J., Hobbs, A. ''Managing maintenance error. A practical guide''. Ashgate publishing company, Hampshire, 2003
 Ray, P.S. et al., Impact of maintenance function on plant safety, Professional Safety, August 2000, pp. 45-48
 Blaise, J.C., ‘Maintenance and safety: analysing maintenance processes and identifying occupational risk factors’, ''Proceedings of the Safety of Industrial Automated Systems Conference,'' Tokyo, 2007, pp. 28-33.
 Grusenmeyer, C., ‘Interactions maintenance-exploitation et sécurité. Etude exploratoire’, Cahier de Notes Documentaires, Hygiène et Sécurité du Travail, N° 186, 2002, pp. 53-66.
 HSE - ''Human factors: Maintenance error''. Retrieved 26 February 2015 from http://www.hse.gov.uk/humanfactors/topics/error.htm
 Okoh, P., Haugen, S., 'A study of maintenance-related major accident cases in the 21st century', ''Process Safety and Environmental Protection'', vol. 92, issue 4, 2014, pp. 346–356
 EU-OSHA – European Agency for Safety and Health at Work, ''Safe maintenance in practice'', 2010. Available at: http://osha.europa.eu/en/publications/reports/safe-maintenance-TEWE10003ENC
 Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast). OJ L 157, 9.6.2006 p. 24.
 Héry, M., ''Copy-editing: La sous-traitance interne'', EDP Sciences, Les Ulis, 2009.
 Nicot, A.M., Rahou, N., ''Place of work and working conditions – France'', 2007. Retrieved 24 June 2011, from: http://eurofound.europa.eu/observatories/eurwork/comparative-information/national-contributions/france/place-of-work-and-working-conditions-France
 INRS – Institut national de recherche et de sécurité, ''Intervention d'entreprises extérieures. Aide mémoire pour la prévention des risques'', ED 941, Paris, 2009. Available at http://www.inrs.fr/media.html?refINRS=ED%20941
EU-OSHA - European Agency for Safety and Health at Work, The human-machine interface as an emerging risk, Available at: https://osha.europa.eu/en/tools-and-publications/publications/literature_reviews/HMI_emerging_risk/view
EFNMS – the European Federation of National Maintenance Societies (website, no publishing date available). Retrieved 26 June 2015 from http://www.efnms.org/
SMRP – Society for Maintenance & Reliability Professionals. Retrieved 26 June 2015 from http://www.smrp.org
Sélectionner le thème