Working at height
Karl Schories, Institute for Occupational Safety and Health of the German Social Accident Insurance
- 1 Introduction
- 2 Safe products and health and safety at work
- 3 Likelihood of accidents and statistical data
- 4 Provision of ‘low risk’ solutions
- 5 Measures and equipment
- 6 References
- 7 Links for further reading
Because of the risk of a fall and potential for serious injury when working at height, measures should be taken to protect against them in the early stages of any project involving work at height. In an individual risk assessment those measures should be selected according to their position in the risk hierarchy: Firstly organizing an alternative working sequence which avoids work at a high elevation; secondly selecting an appropriate technical measure, preferably collective protection and thirdly selecting appropriate personal fall protection.
This article gives hints on different measures and safety devices usable at varying types of workplace and applied procedures for rescuing of casualties after an accident. Reference is made to European Directives forming the legal base.
Safe products and health and safety at work
According to the Council Directives of the European Communities based on the Treaty (Treaty of Nice, amending Treaty of Rome) establishing the European Economic Community (EEC), Article 114, free movement of products must be guaranteed. The directives generally require monitoring procedures to ensure adequate user and third-party protection and typically need other harmonized provisions such as European Standards to cover safety aspects of the products. But it is also stated that this harmonization must happen “without in any way reducing the valid levels of protection already required in the Member States, and provide for any increase herein” (principle of subsidiarity, see, e.g. 89/686/EEC). The European Directives according to the Treaty’s article 114 set out the products’ fundamental provisions necessary for a safer working environment. These directives relate e.g. to personal protective equipment (PPE Directive 89/686/EEC); machinery (Machinery Directive 2006/42/EC - MD) and construction products (Construction Products Directive 89/106/EEC - CPD). Harmonized European Standards following the directives, and usually mandated by the European Committee for Standardisation (CEN), support the practical application.
Provisions for the use of such products and the organization of health and safety at the work place as mentioned in the Treaty’s article 153 are given in several individual directives within the meaning of the framework directive 89/391/EEC, Directive on the introduction of measures to encourage improvements in the safety and health of workers at work (particularly Article 16). The individual directives concern the minimum safety and health requirements, e.g. for the location itself (work place Directive 89/654/EEC); for the use of any tool, apparatus, machine, or installation (work equipment Directive 2009/104/EC, codified version of 89/655/EEC); for the use of personal protective equipment (PPE users’ Directive 89/656/EEC). Concerning the subject of this article, particularly the provisions of Annex 4 within Directive 2009/104/EC will apply. As those directives provide only minimum requirements and any reduction of the existing domestic level of protection has to be excluded from the principle mentioned above, it is up to each European member state how to implement them. Therefore, harmonized standards are dispensable in this context. Particular activities may make it necessary to refer to other directives, e.g. when dealing with electricity or pressure.
Likelihood of accidents and statistical data
Many workplaces still involve the risk of accidents (see table 1).
Obviously the construction sector shows the highest rate. Typical examples of occupation within this sector are construction works of buildings and industrial plants in high elevations, especially maintenance works at roof edges, or installation operations on pylons. But also in other major industries, where frequently high structures and large plants need to be accessed, e.g. for maintenance or the storage and handling of goods, work at height occurs.
The two main risks in this kind of work are falling from an elevated level during access or the work itself followed by being struck from a falling object. It is evident that the rate of mortality increases with the height of the fall. In the forensic study ‘Risk of dying after a free fall from height’, it was reported that the mortality rate was 100% when the falling height was more than 19.2 m (five storeys) but 0% when the falling height was 1.2 m (window-sill) or less. In another published report ‘Injury analysis – data tables’, distinction was made between falls occurring from below two metres (low fall) or above two metres (high fall). From this, it should be noted that these low falls showed a mortality rate of nearly 0.1% and major injuries even gained a rate of nearly 40%.
Moreover, it should be indicated that any work where persons could fall a distance liable to cause injuries is considered to be working at height, but no minimum value (e.g. metres) is generally specified. On the other hand, the definition given formerly for statistical purposes is still commonly accepted. From this, a fall from a height is said to be any fall or slip on an inclined surface steeper than an angle of 45° with a vertical measured distance of at least one metre. However, limiting values and definitions may vary between European countries because of the principle of subsidiarity. That means that it is up to each member state to organize safety at work under their own responsibility, but the minimum requirements given in the European Directives have to be met (see above, ‘Safe products and health and safety at work’)
Among all fall accidents, the situation where a person used a ladder was identified to be the most hazardous, because they were to be more than 25% of the total number of falls. Other notable agents were the following: plant, large vehicles and machines (>20%); scaffolds (10%); hoisting and storage devices (<10%); office equipment, personal equipment and furniture (<10%); edges and openings at roofs and floors (5%); partitions, materials and other objects (5%); stairs and steps (>5%). These distributions did not vary too much all over Europe, but a significant difference could be seen in the absolute values in the different European countries, depending on the number of inhabitants. However, it seemed that there was a slight upward trend in the rates of accidents from northern Europe to southern Europe, see ‘European comparison – Background and data sources’.
Provision of ‘low risk’ solutions
Avoid working at height
Out of the number of solutions which are generally possible, a selection should be made which provides the lowest risk. To achieve this, the first step should be an identification of existing hazards, when coming to practical work situations. Workplaces should be examined regarding their properties, the activities to be done there and the nature and state of the access. At this stage, the question, of whether it is possible to avoid working at height totally, or more likely in part, should be taken into account.
Instead of assembling the members of a roof construction at roof height, it might be convenient to assemble them into larger units at ground level on the site and then lift them by crane, where they can be joined together to form the complete roof in a short-time activity. Additional prefabrication in the work shop should be discussed, implicating the boundary conditions, e.g. profit in quality, area of utilization at the construction site, useable roads and urban traffic, capacity of the crane at the staff’s disposal on site. Simultaneously the risks of any workplace transport should be considered.
When looking at maintenance works (e.g. window cleaning, storage of goods, etc.), sometimes the use of simple handling devices can assist in providing alternative working sequences which can be done from the floor.
After the decision is made on which work is to be done at height, a safe location and environment needs to be provided. Furthermore, it is essential that the work is done by a qualified and competent employee.
Collective fall protection
The next step should follow the risk hierarchy and be to check the possibility and convenience of using any appropriate collective fall protection, e.g. to prevent access to edges or fragile surfaces (roof lights, roof coverings or areas in slabs of poor resistance, other potentially hazardous surfaces, etc.) Furthermore, the situation at ground level (e.g. uneven, partially covered or even crowded); the employees’ physical burden during their working sequence; dependence on weather conditions or environmental factors should be considered within this check.
As a relating example:
A roof with moderate inclination of an industrial plant is to be sheeted using trapezoidal corrugated metal elements of large dimensions. Because of the wide opening along the edge where the sheets are being placed continuously and the fast progress of the work, the employees on the roof should be protected by a collective system. Here the installation of a safety net system S (in accordance with European Standard EN 1263-1) is recommended. The net is situated slightly beneath the roof level covering the entire floor area. Because of this, any installation work done on the ground level simultaneously would not be affected, if the eaves’ plane is high enough and clearance beneath the safety net is sufficient. Furthermore, the edges along the eaves quickly become longer, depending on the progress of the work. Commonly, the partly completed roof is used as a traffic area for access and transport and also to store materials (in this example, metal sheets and fixing elements) intermediately. To prevent any fall over the edges along eaves and verges where the sheeting is already placed, a temporary edge protection system (in accordance with European Standard EN 13374) should be assembled to match the progress of the work, as long as no façade scaffold is still ready for use. If no protection system can be applied directly at the roof edge, e.g. during working at the edge, an intercepting device like a bracket supported safety net or a working platform with side protection may be provided beneath verges and eaves.
Another collective method to protect the employees from fall to the floor – especially when there is a lack in height for netting – is the assembly of falsework made of scaffolding components with platforms laid out beneath the roof level. This intercepting scaffold should cover at least the area along the edge of the working area and may be moved, depending on work’s progress. A construction like this is also useful for work to be done on the ceiling and on high walls. In a situation where there is no necessity for a large effective range, a mobile access tower (MAT) may be sufficient. Otherwise, a mobile elevating work platform (MEWP) can provide more flexibility. However, careful attention should be paid to the manual provided by the manufacturer when using such devices. Particular care is important here with respect to a complete and capable guard rail around the platform and the entire stability of the MEWP, depending among others on the conditions at ground level. Working on a ladder should be avoided as far as possible and only be allowed for substantiated practical reasons. The use of a ladder may be accepted in some circumstances, e.g. when for any short-time tasks (commonly less than 30 minutes) no other means can be made available within a reasonable period.
Personal fall protection
If a working sequence at an elevated position cannot be done at or from the ground level and the provision of effective barriers such as guard rails at this position has to be excluded for reasons pertaining to the work sequence itself and intercepting devices such as safety nets are not appropriate because of the particularities of the project, personal fall protection would need to be used. Also in a situation where an alternative working sequence and the installation of technical measures will increase the risk generally, personal protective equipment (PPE) should be used to follow the principle of lower risk. However, the effect of PPE depends on the competence of the employee, his sense of responsibility and his physical and mental fitness.
Another example is given here:
Latticed steel towers for high voltage energy supply, known as transmission towers or more colloquially, electricity pylons, are exposed to considerable atmospheric effects. Therefore, they have to be maintained periodically. Following the above mentioned principles, the use of PPE is reasonable for this kind of work. While ascending the pole, the employee may be secured by his safety harness and a twin-tailed lanyard. This lanyard has one end with a customary karabiner to be fixed to the safety harness and two ends with scaffold hooks for connection to the structure. At least one connection, not lower than the position of the employee, should always be maintained. More frequently nowadays, a method of rope ascending, positioning and descending is the favoured method, where double security is provided by a main rope and a safety rope (working line and safety line). Anyway, for the purpose of installation of the main rope running from the base of the tower to the cross arms, usually twin-tailed lanyards are still needed. Additional care has to be taken on live wires to avoid any current pulse. Temporary disconnection of the circuit – right or left sided respectively – is necessary depending on the actual work sequence.
Means of access
The decision on which kind of means of access to choose should follow a similar premise as mentioned above with the location: a safe installation or equipment should be provided! In this step, it is advantageous to look for an already (or still) existing installation for permanent (or temporary) use. If that does not exist, a temporary staircase, e.g. an aluminium tower scaffold, should be installed in preference to using a ladder. This may be stated particularly with a view to roof construction, see the previous example. In a multi-storey building, it may be convenient to use a mast climbing access platform during the construction period until the shell is completed. Later on, e.g. when there are still some single or short-time activities left to be done, a mobile elevating work platform (MEWP) might fit. But also with this work equipment, attention should be paid on the effectiveness of relating fall protection facilities. In some cases, additional protection, e.g. a restraint system, is appropriate on an elevated platform. On the other hand, the last example from above shows that there are several cases where the access needs the same kind of fall protection (e.g. PPE) as when doing the work itself.
The extent of requirements for the first aid and emergency system on site increases accordingly with the prevention measure’s position in the risk hierarchy, see above. No extra requirements are needed as long as work is always done from ground level. As long as effective measures (of immediate effect, like capable barriers or edge protection systems) would prevent any fall, only foreseeable misuse would need to be taken into account additionally. If collective protection of the intercepting type is projected, the provision of a description on how to rescue a fallen person from the device is required, too. This might imply also organizing measures, like the stipulation of team work only. With the use of personal fall protection, it is a legal requirement to implement procedures and awareness for a rapid and efficient rescue. Any delay could affect the casualty’s health seriously in case of emergency, including when suspended in a safety harness after falling. Further description of consequences and rules for first aid and subsequent attendance may be obtained from ‘Guide to the safety, health and welfare at work’.
The user’s manual – which has to be available on site – should give precise information on the subject and should be enhanced according to expanding experience. Depending on the variety of constructions and situations, e.g. latticed steel towers, supporting framework of a power plant’s boiler, masts of wind turbines, or scaffolds at gothic cathedrals, special equipment (accompanied with a user’s manual including all relevant information, supplied by the manufacturer) is frequently necessary for the rescue of casualties after a fall.
The general hints and examples given here should be helpful when preparing the mandatory risk assessment although they are not exhaustive. Additionally, see ‘Slipping and falling from a height’, where an extended check list for determining the risks and a guide for risk assessment is included. For a last check for scaffolds and ladders before the work starts, see for a short list provided on the web site of the European agency for safety and health at work. Other helpful hints might be obtained here from the section on construction. Moreover, there are practice reports on experience gained from construction sites available – published by EU-OSHA or in periodical health and safety magazines – see ‘Links for further reading’ below.
Measures and equipment
As mentioned above, an adequate employment of measures and selection of equipment concerning health and safety at work depends basically on the national legal implementation of the provisions given in the European Directives on the subject and particularly on the risk assessment as for the individual case. Furthermore, the application of the given examples does not always apply all over Europe due to national deviations in the respective rules. The following compilation, given in a safety-related order, might help further.
Methods where work at high elevation can be avoided
Extensive pre-assembly, useful if construction members foreseen in upper levels are numerous and as long as a capable lifting device is available (picture 1).
Installation of a pulley to allow for lowering objects, e.g. equipment which needs maintenance periodically like lighting in a work shop, to the floor or ground level; Use of extendable equipment to reach objects to be maintained or handled from the floor or ground level, e.g. for cleaning windows situated not higher than in the first storey when cleaning from the outside; cleaning gutters of a dwelling house; or cutting branches from a tree.
Methods preventing any fall
Use of metallic or wooden fencing structures or guardrails supported by posts providing a resistant barrier (see picture 2) along excavations, fragile surfaces, openings (e.g. in slabs), or edges (e.g. of flat roofs or where the angle of inclination is not more than 20°, at verges), etc. – if no integral fence is used here, the minimum provisions should comprise a principal guardrail (at a height of one metre at least), an intermediate guardrail, and a toeboard.
Closure and bridging of present openings, e.g. in floors, by coverings – such as timber planks, steel plates, grating decks, or perforated metal planks, with appropriate support where necessary – fulfilling the requirements relating to serviceability and resistance according to the expected live load, including an adequate edge protection. At temporary bridges used as means of access on site, further protection (barrier-like as mentioned before or interceptive as seen below) is necessary.
Assembly of a scaffold (or a MAT for shorter periods of application) establishes a secured workplace at facades and a means of access, too – where the general requirements concerning the requirements for guardrails should side protection shall be as described above); Selection of elevating platforms (preferably MEWPs in case of short-time use), which provide a workplace and a mean of access as well – but bearing in mind that devices for lifting persons more than three metres are “hazardous” machines in the sense of Machine Directory, Annex IV, their conformity with the essential health and safety requirements has to be assessed, based on the relevant European Standard) or, alternatively, a complete type-examination involving a notified body is required.
Collective fall protections preventing a deeper fall
Edge protection systems assembled at eaves of inclined roofs (slope angle more than 20°) – if the length from eaves to ridge is more than five metres, an intermediate barrier on the roof is required additionally – providing enough strength to protect a person who slides or falls into the protection.
Safety net systems positioned beneath a worksite where there could be a fall from a height covering the entire floor and being fixed to the existing structure (System S),(see picture 3) or covering only the necessary fall-catching area and being spread in a separate system-belonging construction, e.g. brackets (System T), cantilevers or frames (System V);
Intercepting scaffolds with configurations analogous to the safety net systems mentioned above may be assembled instead of netting, if they are going to be used for other tasks anyway, or if there would be too little clearance beneath a net – depending on the construction’s height and the local conditions. Net-based working platforms may perform an alternative to the latter configuration, e.g. where circumstances exclude the assembly of a falsework; but with this system, a solid construction – with members like steel girders with a large section – which allows for pre-tension of the platform net is required, as described in ‘Net-based working platforms for use at high elevations’.
Personal fall protection
Personal fall protection may be used if tasks in elevated situations cannot be organized avoiding work at a height and collective measures have been excluded for technical reasons or because their assembly is riskier than doing the work at height and using personal protective equipment (PPE). PPE – particularly PPE against falls from a height – has to be manufactured, third-party tested and certified in accordance with the PPE Directive, and its classification therein. In practice, relevant harmonized European Standards as those are listed by the European Commission, in the Official Journal (OJEU) are generally used to assist this process.
The types of personal fall protection systems commonly available are summarized below:
- Fall arrest systems (harness, lanyard, connector, fall arrester);
- restraint systems (belt, lanyard, connector, fixing point or - member);
- workplace positioning systems (harness, lanyard – additionally main rope, if used in combination with the following system – connector, anchor point or solid member);
- ascending and descending systems, e.g. a rope access system (harness, lanyard, main rope, safety rope, connector, anchor point or solid member).
Structural anchors and members used as an attachment point should be verified by test or calculation with respect to an adequate design load according to CPD and subsequent regulations, because they are not covered by the PPE Directive.
Equipment for access and use as a workplace at a height
Most accidents occur with equipment that is meant to access a workplace and is also used as a workplace, particularly with ladders. Attention should be paid to instruction manuals, which are required be available on site. Although most examples of these equipments have been already mentioned before, a short list is given here in finalizing this compilation:
- Mobile access towers (MATs): It should be stated clearly, that when working from a MAT (see picture 4), moving the device e.g. to another location, is only allowed after the employee has descended;
- Mobile elevating work platforms (MEWPs), (see above and example for roofing in 3.2 Collective fall protection);
- Suspended access and positioning devices (e.g. working platforms, - baskets or seats), usually to be lifted by crane, as well as the personal access systems (see above and clause 3) may be implemented where extreme conditions would not justify any other – surely less hazardous – solution;
- Portable ladders – most commonly known as leaning rung ladders or standing step ladders – when used as a means of access may only be used for single tasks within short periods: Fixed ladders as a permanent means of access should be used together with rigid anchor lines for the use of a guided type fall arrester, in accordance with relevant standards, in order to decrease risk. The use of safety cages when installed instead of rigid anchor lines should include the installation of intermediate platforms, if the ladder flight exceeds six metres. Research has shown recently that safety cages themselves offer no or only marginal protection.
- EC – European Commission (ed.), ’Causes and circumstances of accidents at work’, European Commission DG Employment, Social Affaires and Equal Opportunities, Luxembourg, 2009. Available at http://ec.europa.eu/social/main.jsp?catId=738&langId=en&pubId=207&furtherPubs=yes
- Risser, D., Bönsch A., Schneider B., Bauer G., ‘Risk of dying after a free fall from height’ Forensic Science International, Vol. 78, 1996 pp. 187-191,
- HSE – Health and Safety Executive (ed.), ‘Injury analysis – data tables’, Health and Safety Executive, United Kingdom, 2009. Available at: http://www.hse.gov.uk/statistics/tables/index.htm#riddor
- Hoffmann, B. and Noetel, K.-H., ‘Unfälle von Schornsteinfegern’, Die BG 1988, S. 380-384, Erich Schmidt Verlag, Bielefeld, 1988. (in German).
- DGUV – Deutsche Gesetzliche Unfallversicherung, Referat ‘Statistik – Makrodaten, Arbeits- und Schülerunfälle’,(ed), ‘ Berichtsjahr 2005-2009 – Meldepflichtige Arbeitsunfälle im Betrieb – Unfälle bei baulichen Einrichtungen in der Höhe’, München, 2010 (in German).
- HSC – Health and Safety Commission, (ed.), ‘Statistics of workplace fatalities and injuries – Falls from a height’ United Kingdom, 2009. Available at: http://www.hse.gov.uk/statistics/pdf/rhsfall.pdf
- HSE – Health and Safety Executive (2010), ‘Statistics – European comparison – Background and data sources’. Retrieved 10 October 2011, from: http://www.hse.gov.uk/statistics/european/background.htm
- EN 1263-1:2002 ‘Safety nets – Part 1: Safety requirements, test methods’. Available at: http://www.markosweb.com/www/standardsdirect.org/ (webshop).
- EN 13374: 2004 ‘Temporary edge protection systems – Product specification, test methods’. Available at: http://www.markosweb.com/www/standardsdirect.org/ (webshop).
- Wikipedia, the Free Encyclopedia (20 June 2011), Falsework. Retrieved on 14 October 2011, from: http://en.wikipedia.org/wiki/Falsework.
- Edeler, J., ‘Schutz gegen Absturz – Korrosionsschutzarbeiten auf Gittermasten’, BAU BG aktuell 2/2000, Bau BG Rheinland und Westfalen, Wuppertal, 2000, pp.16-18 (in German).
- Ottersbach, J., Schäper, W., ‘Ermittlung von Fangstoßkräften bei der Verwendung von Rückhaltesystemen in Arbeitskörben von Hubarbeitsbühnen’, Präsentation zum Fachgespräch Maschinenschutz, Institut für Arbeitsschutz, Sankt Augustin, 2010. (in German).
- HSA – Health and Safety Authority, (ed.), ‘Guide to the safety, health and welfare at work (Work at height)’, Health and Safety Authority, Ireland, 2006.
- ISSA – International Social Security Association; Section Electricity, Gas and Water (ed.), ’Slipping and falling from a height’, International Social Security Association, Germany, 2009. Available at: http://www.issa.int/Resources/Resources/Slipping-and-Falling-from-A-Height
- EU-OSHA – European Agency for Safety and Health at Work (no publishing date available), Scaffolds and ladders — a checklist. Retrieved 12 September 2011, from http://osha.europa.eu/en/sector/construction/scaffolds
- ZS Bau BG – Zentrum für Sicherheitstechnik der Bau-Berufsgenossenschaft Rheinland und Westfalen (ed.), ‘Practical guidelines for preventing falls from a height’, EU project no. FFFF0206, Zentrum für Sicherheitstechnik der Bau-Berufsgenossenschaft Rheinland und Westfalen, Erkrath, 2002.
- EN 12811-1: 2003 ‘Temporary works equipment – Part 1: Scaffolds – Performance requirements and general design’. Available at: http://www.markosweb.com/www/standardsdirect.org/ (webshop).
- EN 280:2001 ‘Mobile elevating work platforms – Design calculations – Stability criteria – Construction – Safety – Examinations and tests’. Available at: http://www.markosweb.com/www/standardsdirect.org/ (webshop).
- Schories, K., ‘Net-based working platforms for use at high elevations’, Focus on BGIA’s Work No. 259, Institut für Arbeitsschutz, Sankt Augustin, 2006.
- EN ISO 14122-1:2001 ‘Safety of machinery – Permanent means of access to machinery – Part 1: Choice of fixed means of access between two levels. Available at: http://www.markosweb.com/www/standardsdirect.org/ (webshop).
- EN 353-1: 2002 ‘Personal protective equipment against fall from a height – Part 1: Guided type fall arresters including a rigid anchor line’. Available at: http://www.markosweb.com/www/standardsdirect.org/ (webshop).
Links for further reading
Andersson, K.-G., ’Working at height – Are you properly protected?’, Health and Safety International, Oct. 2004. Available at: http://www.hsimagazine.com/article.php?article_id=281
Dymott, R., ‘Working at height – Windmills ... but not as you know them!’, Health and Safety International, Nov. 2009. Available at: http://www.hsimagazine.com/article.php?article_id=372
EU-OSHA – European Agency for Safety and Health at Work (ed.), ‘Preventing falls of carpenters’, in: Success is no accident – Accident prevention in practice, European Agency for Safety and Health at Work, Luxembourg, 2001. Available at: http://osha.europa.eu/en/publications/reports/103/view
EU-OSHA – European Agency for Safety and Health at Work (ed.), ‘Work at height – Fall protection during roof work’, in: Building in safety – Prevention of risks in construction – in practice, European Agency for Safety and Health at Work, Luxembourg, 2004. Available at: http://osha.europa.eu/en/publications/reports/108/view
EU-OSHA – European Agency for Safety and Health at Work (ed.), ‘Improvement of safety when carrying out work at height’, in: Building in safety – Prevention of risks in construction – in practice, European Agency for Safety and Health at Work, Luxembourg, 2004. Available at: http://osha.europa.eu/en/publications/reports/108/view
EU-OSHA – European Agency for Safety and Health at Work (ed.), ‘Prevention of falls from a height on construction sites (Latvia)’, in: Achieving better safety and health in construction – Information report, European Agency for Safety and Health at Work, Luxembourg 2004. Available at: http://osha.europa.eu/en/publications/reports/314/view
Harris, R., ‘Safety nets for working at height’, Health and Safety International, Apr. 2005. Available at: http://www.hsimagazine.com/article.php?article_id=229
Herold, K., ‘Seilunterstütztes Retten und Bergen in Höhen und Tiefen’, Technische Universität Chemnitz, Maschinenbau, Arbeitswissenschaft / Institut für Arbeitsschutz (Hrsg.), Chemnitz / Sankt Augustin, 2006. (in German).
HSA – Health and Safety Authority, (ed.), ‘Safety, Health and Welfare Act 2005 (No. 10 of 2005)’, Health and Safety Authority, Ireland, 2006. Available at: http://www.hsa.ie/eng/Legislation/Acts/Safety_Health_and_Welfare_at_Work/
IOSH – Institution of Occupational Safety and Health (2011), ’Guidance: What you need to know – Working at height’. Retrieved 12 September 2011 from http://www.iosh.co.uk/news_and_events/connect/39_working_at_height.aspx
Krüger B., Gehbauer F., Klampfl R., Rickers U. ‘Seilunterstützte Zugangstechniken für den Einsatz im Bauwesen’, Bautechnik 84, , Ernst & Sohn, Berlin, 2007. pp. 499-502. (in German).
Saìz, J. and Schories, K., ‘Testing of safety nets in the construction sector under particular consideration of the ageing of the safety nets in Germany and Spain’, International Fall Protection Symposium, Wuppertal 1998, abstracts, HVBG/ZS Erkrath, 1998, p. 102. Thomas, D., ‘Fall arrest equipment’, Health and Safety International, Oct., 2007. Available at: http://www.hsimagazine.com/article.php?article_id=112