ISO 13849-1 Analysis — Part 6: CCF — Common Cause Failures

This entry is part 6 of 6 in the series How to do a 13849-1 analysis

What is a Common Cause Failure?

There are two similar-sounding terms that people often get confused: Common Cause Failure (CCF) and Common Mode Failure. While these two types of failures sound similar, they are different. A Common Cause Failure is a failure in a system where two or more portions of the system fail at the same time from a single common cause. An example could be a lightning strike that causes a contactor to weld and simultaneously takes out the safety relay processor that controls the contactor. Common cause failures are therefore two different manners of failure in two different components, but with a single cause.

Common Mode Failure is where two components or portions of a system fail in the same way, at the same time. For example, two interposing relays both fail with welded contacts at the same time. The failures could be caused by the same cause or from different causes, but the way the components fail is the same.

Common-cause failure includes common mode failure, since a common cause can result in a common manner of failure in identical devices used in a system.

Here are the formal definitions of these terms:

3.1.6 common cause failure CCF

failures of different items, resulting from a single event, where these failures are not consequences of each other

Note 1 to entry: Common cause failures should not be confused with common mode failures (see ISO 12100:2010, 3.36). [SOURCE: IEC 60050?191-am1:1999, 04-23.] [1]

 

3.36 common mode failures

failures of items characterized by the same fault mode

NOTE Common mode failures should not be confused with common cause failures, as the common mode failures can result from different causes. [lEV 191-04-24] [3]

The “common mode” failure definition uses the phrase “fault mode”, so let’s look at that as well:

failure mode
DEPRECATED: fault mode
manner in which failure occurs

Note 1 to entry: A failure mode may be defined by the function lost or other state transition that occurred. [IEV 192-03-17] [17]

As you can see, “fault mode” is no longer used, in favour of the more common “failure mode”, so it is possible to re-write the common-mode failure definition to read, “failures of items characterised by the same manner of failure.”

Random, Systematic and Common Cause Failures

Why do we need to care about this? There are three manners in which failures occur: random failures, systematic failures, and common cause failures. When developing safety related controls, we need to consider all three and mitigate them as much as possible.

Random failures do not follow any pattern, occurring randomly over time, and are often brought on by over-stressing the component, or from manufacturing flaws. Random failures can increase due to environmental or process-related stresses, like corrosion, EMI, normal wear-and-tear, or other over-stressing of the component or subsystem. Random failures are often mitigated through selection of high-reliability components [18].

Systematic failures include common-cause failures, and occur because some human behaviour occurred that was not caught by procedural means. These failures are due to design, specification, operating, maintenance, and installation errors. When we look at systematic errors, we are looking for things like training of the system designers, or quality assurance procedures used to validate the way the system operates. Systematic failures are non-random and complex, making them difficult to analyse statistically. Systematic errors are a significant source of common-cause failures because they can affect redundant devices, and because they are often deterministic, occurring whenever a set of circumstances exist.

Systematic failures include many types of errors, such as:

  • Manufacturing defects, e.g., software and hardware errors built into the device by the manufacturer.
  • Specification mistakes, e.g. incorrect design basis and inaccurate software specification.
  • Implementation errors, e.g., improper installation, incorrect programming, interface problems, and not following the safety manual for the devices used to realise the safety function.
  • Operation and maintenance, e.g., poor inspection, incomplete testing and improper bypassing [18].

Diverse redundancy is commonly used to mitigate systematic failures, since differences in component or subsystem design tend to create non-overlapping systematic failures, reducing the likelihood of a common error creating a common-mode failure. Errors in specification, implementation, operation and maintenance are not affected by diversity.

Fig 1 below shows the results of a small study done by the UK’s Health and Safety Executive in 1994 [19] that supports the idea that systematic failures are a significant contributor to safety system failures. The study included only 34 systems (n=34), so the results cannot be considered conclusive. However, there were some startling results. As you can see, errors in the specification of the safety functions (Safety Requirement Specification) resulted in about 44% of the system failures in the study. Based on this small sample, systematic failures appear to be a significate source of failures.

Pie chart illustrating the proportion of failures in each phase of the life cycle of a machine, based on data taken from HSE Report HSG238.
Figure 1 – HSG 238 Primary Causes of Failure by Life Cycle Stage

Handling CCF in ISO 13849-1

Now that we understand WHAT Common-Cause Failure is, and WHY it’s important, we can talk about HOW it is handled in ISO 13849-1. Since ISO 13849-1 is intended to be a simplified functional safety standard, CCF analysis is limited to a checklist in Annex F, Table F.1. Note that Annex F is informative, meaning that it is guidance material to help you apply the standard. Since this is the case, you could use any other means suitable for assessing CCF mitigation, like those in IEC 61508, or in other standards.

Table F.1 is set up with a series of mitigation measures which are grouped together in related categories. Each group is provided with a score that can be claimed if you have implemented the mitigations in that group. ALL OF THE MEASURES in each group must be fulfilled in order to claim the points for that category. Here’s an example:

A portion of ISO 13849-1 Table F.1.
ISO 13849-1:2015, Table F.1 Excerpt

In order to claim the 20 points available for the use of separation or segregation in the system design, there must be a separation between the signal paths. Several examples of this are given for clarity.

Table F.1 lists six groups of mitigation measures. In order to claim adequate CCF mitigation, a minimum score of 65 points must be achieved. Only Category 2, 3 and 4 architectures are required to meet the CCF requirements in order to claim the PL, but without meeting the CCF requirement you cannot claim the PL, regardless of whether the design meets the other criteria or not.

One final note on CCF: If you are trying to review an existing control system, say in an existing machine, or in a machine designed by a third party where you have no way to determine the experience and training of the designers or the capability of the company’s change management process, then you cannot adequately assess CCF [8]. This fact is recognised in CSA Z432-16 [20], chapter 8. [20] allows the reviewer to simply verify that the architectural requirements, exclusive of any probabilistic requirements, have been met. This is particularly useful for engineers reviewing machinery under Ontario’s Pre-Start Health and Safety requirements [21], who are frequently working with less-than-complete design documentation.

In case you missed the first part of the series, you can read it here. In the next article in this series, I’m going to review the process flow for system analysis as currently outlined in ISO 13849-1. Watch for it!

Book List

Here are some books that I think you may find helpful on this journey:

[0]     B. Main, Risk Assessment: Basics and Benchmarks, 1st ed. Ann Arbor, MI USA: DSE, 2004.

[0.1]  D. Smith and K. Simpson, Safety critical systems handbook. Amsterdam: Elsevier/Butterworth-Heinemann, 2011.

[0.2]  Electromagnetic Compatibility for Functional Safety, 1st ed. Stevenage, UK: The Institution of Engineering and Technology, 2008.

[0.3]  Overview of techniques and measures related to EMC for Functional Safety, 1st ed. Stevenage, UK: Overview of techniques and measures related to EMC for Functional Safety, 2013.

References

Note: This reference list starts in Part 1 of the series, so “missing” references may show in other parts of the series. The complete reference list is included in the last post of the series.

[1]     Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design. 3rd Edition. ISO Standard 13849-1. 2015.

[2]     Safety of machinery — Safety-related parts of control systems — Part 2: Validation. 2nd Edition. ISO Standard 13849-2. 2012.

[3]      Safety of machinery — General principles for design — Risk assessment and risk reduction. ISO Standard 12100. 2010.

[8]     S. Jocelyn, J. Baudoin, Y. Chinniah, and P. Charpentier, “Feasibility study and uncertainties in the validation of an existing safety-related control circuit with the ISO 13849-1:2006 design standard,” Reliab. Eng. Syst. Saf., vol. 121, pp. 104–112, Jan. 2014.

[17]      “failure mode”, 192-03-17, International Electrotechnical Vocabulary. IEC International Electrotechnical Commission, Geneva, 2015.

[18]      M. Gentile and A. E. Summers, “Common Cause Failure: How Do You Manage Them?,” Process Saf. Prog., vol. 25, no. 4, pp. 331–338, 2006.

[19]     Out of Control—Why control systems go wrong and how to prevent failure, 2nd ed. Richmond, Surrey, UK: HSE Health and Safety Executive, 2003.

[20]     Safeguarding of Machinery. 3rd Edition. CSA Standard Z432. 2016.

[21]     O. Reg. 851, INDUSTRIAL ESTABLISHMENTS. Ontario, Canada, 1990.

Five things you need to know about CE Marked Wire and Cable

Wire is simple right? Maybe not! Here are the top five things to know when selecting wire and cable products for use in designs that will be CE Marked:

  1. Wire and cable products sold in the EU must be CE Marked under the Low Voltage Directive, and MAY bear BOTH the CE Mark and the HAR mark. The HAR mark may only be applied by manufacturers that have met the requirements for the use of the HAR mark. More information on the HAR mark. 

    Picture of the HAR Mark.
    The HAR Mark
  2. The HD 21.X and HD 22.X Harmonization Documents previously used for determining compliance and applying the CE Mark are being replaced by the EN 50525.X family of standards starting on 2014-01-17. See the list.
  3. Wire and Cable products with Declarations of Conformity that refer to older versions of the Low Voltage Directive, or that refer to HD documents that have been superseded are NO LONGER COMPLIANT.
  4. Wire and Cable products used in “large-scale” machine tools and fixed installations do not need to meet WEEE requirements.
  5. Designers are not required to use CE Marked wire and cable products in CE Marked Products.

Need to know more? Check out this article!

CE Marking Wire and Cable – Necessity or Luxury?

When I set out to investigate the need for CE Marks and <HAR> marks on wire and cable products, I would not have guessed that it would turn out to be as much of an odyssey as it did. For most products, determining the need for a CE Mark is relatively straightforward, but not for wire and cable products! As equipment designers, engineers and technologists, we rarely think much about wire and cable. We’re mostly concerned with the insulation colours, number of conductors, the gauge, and the voltage rating. Sometimes we’re also concerned about the temperature rating, the flexibility, or perhaps the shielding. The regulatory approvals carried by the wire are often assumed, or not considered at all. This common product can bring a world of headaches if the requirements are not fully considered.

Regulatory Requirements

North America

In North America, the three main regulatory organizations for electrical component safety certifications are UL, CSA, and NOM. All three publish standards applicable to wire and cable, and the markings and common wire styles, like TEW, AWM, MTW, and SOW, are driven by these standards.

Europe – HAR Marking

What about Europe? The EU has a separate system for identifying wire and cable, identified by the HAR Mark. Learn more about this mark.

Picture of the HAR Mark.
The <HAR> Mark

The HAR mark, which stands for “Harmonised”, has been based on the application of Harmonised Documents (HD) published by CENELEC, including the HD 21.X and HD 22.X families, which was replaced by the EN 50525 series of standards effective 2014-01-17. But what is the basis for marking, and is there a legal requirement for manufacturers to use marked wire? The HAR Mark is one of the earliest common marks in the EU, originating from an agreement signed in 1974. Manufacturers who wish to use the HAR Mark are required to meet stringent quality control requirements before being granted the right to use the HAR mark. Wire and cable products bearing the HAR mark are accepted by all of the signatory states to the HAR agreement. (Need to know more? Have a look at the EEPCA web site.) The HAR mark is not legally required, but using products bearing the HAR Mark may make a manufacturer’s life a bit easier when dealing with authorities.

Europe – CE Marking

What about the CE Mark for wire and cable?  To answer that question, we need to look at the CE Marking requirements in more detail. In general, CE Marking Directives are aimed at products, not at components, although there are some exceptions. Wire and cable products are one of those exceptions that stand out. On its own, wire or cable has no defined use or application, in that it must be built into something to be useful. The compliance of the final product containing the wire products is determined based on testing related to the finished product, and the compliance of the wire used in the product is based on the specific application and the wire product’s performance in that product. So why are wire and cable products CE Marked on their own?

Determining the Right Directives

Most directives require that products within the scope have some defined function, like the Machinery Directive’s definition of a machine:

“…an assembly, fitted with or intended to be fitted with a drive system other than directly applied human or animal effort, consisting of linked parts or components, at least one of which moves, and which are joined together for a specific application…”, [1]

or the EMC Directive definition of “apparatus”:

“…‘apparatus’ means any finished appliance or combination thereof made commercially available as a single functional unit, intended for the end user and liable to generate electromagnetic disturbance, or the performance of which is liable to be affected by such disturbance…” [2]

Clearly, these definitions don’t include components. So what directives do apply to wire products? The first directive that comes to mind is the Low Voltage Directive. If we take a look at the definitions in the Directive [3] we find:

Article 1

For the purposes of this Directive, ‘electrical equipment’ means any equipment designed for use with a voltage rating of between 50 and 1 000 V for alternating current and between 75 and 1 500 V for direct current, other than the equipment and phenomena listed in Annex II.

Once again, we have a pretty specific definition for the target of the Directive: “electrical equipment”. Or do we? What, exactly, is “electrical equipment”? The Directive doesn’t define this term, but it does give us a list of exclusions in Annex II [3]:

Annex II

  • Equipment and Phenomena outside the Scope of this Directive
  • Electrical equipment for use in an explosive atmosphere
  • Electrical equipment for radiology and medical purposes
  • Electrical parts for goods and passenger lifts
  • Electricity meters
  • Plugs and socket outlets for domestic use
  • Electric fence controllers
  • Radio-electrical interference
  • Specialised electrical equipment, for use on ships, aircraft or railways, which complies with the safety provisions drawn up by international bodies in which the Member States participate.

At this point, it doesn’t look like wire products are included in the directive. No further definition of “electrical equipment” is given, and wire and cable are not specifically excluded in Annex II. Where do we go from here to better understand the definition of “electrical equipment”?

The IEC publishes the International Electrotechnical Vocabulary (IEV), IEC 60050 [4], defining hundreds of terms related to electro-technical topics. This is the next logical step in trying to understand what is covered. Definitions in the IEV are numbered as a means to catalog the terms, and I’ve provided the definition numbers for reference. Unfortunately, the IEV does not contain a definition for “electrical equipment”, but it does define “equipment” [3, 151-11-25]:

equipment – single apparatus or set of devices or apparatuses, or the set of main devices of an installation, or all devices necessary to perform a specific task

Note – Examples of equipment are a power transformer, the equipment of a substation, measuring equipment.

The definition uses the term “apparatus”, which continues the lack of clarity. Is wire apparatus? Looking up the definition for “Apparatus” 151-11-22, the IEV gives us:

apparatus – device or assembly of devices which can be used as an independent unit for specific functions

Note – In English, the term “apparatus” sometimes implies use by skilled persons for professional purposes.

Wire clearly doesn’t meet the definition for apparatus, since it couldn’t be considered and “independent unit for a specific function”, so is wire a device? Now we have one more term to try to understand. The definition for “device” is found in the IEV at 151-11-20:

device – material element or assembly of such elements intended to perform a required function

Note – A device may form part of a larger device.

Now we’re getting somewhere. Wire could definitely be considered to be a “material element”, but we’re stuck again at the need to “perform a required function”. One more term might apply. Let’s look at “components”. The definition for a “component” is found at 151-11-21:

component – constituent part of a device which cannot be physically divided into smaller parts without losing its particular function

Now we’ve got it! Wire is clearly a component, and this clearly makes sense when you consider the use we make of wire and cable products. But how does this relate back to the legal definition of “electrical equipment”? Since the IEV is not called out by the Directive, we can’t lean on this definition alone to decide the applicability of the CE Mark to these products.

Low Voltage Directive Requirements

The EU Commission publishes a Guide for most of the Directives, and the Low Voltage Directive is no different. There is little direct reference to wire and cable products, however, [5, para. 8] does mention it in broad terms, “…the Directive covers consumer and capital goods designed to operate within those voltage limits, including in particular, …electrical wiring, appliance couplers and cord sets…” [5, Annex II] provides a pictorial list of products, illustrating the cord set requirement. Within the voltage limits set by the scope of the LVD, the requirement for cord sets and other “safety critical” sub-assemblies that include wire or cable makes sense. A completed cord set with an IEC 320 connector on one end and a country specific plug, like a a CEE plug cap, is a complete product with a defined end-use, and so fits the scope. This seems to answer the original question: “Do wire & cable products, on their own, require a CE Mark?”, at least under the LVD. The next question must be: “Are there any other CE Marking Directives that might apply?”

RoHS and WEEE Directives

We can exclude the EMC Directive, since the definition of apparatus in that directive is quite clear. What about RoHS [6], and WEEE [7]? Let’s look at RoHS and WEEE together, since these two Directives are linked in application. The 2011 RoHS directive [8] includes some definitions of what electrical and electronic equipment is, and includes two key definitions for machine builders:

Article 3 

Definitions

For the purposes of this Directive, the following definitions shall apply:

  1. electrical and electronic equipment’ or ‘EEE’ means equipment which is dependent on electric currents or electromagnetic fields in order to work properly and equipment for the generation, transfer and measurement of such currents and fields and designed for use with a voltage rating not exceeding 1 000 volts for alternating current and 1 500 volts for direct current; 
  2. for the purposes of point 1, ‘dependent ‘ means, with regard to EEE, needing electric currents or electromagnetic fields to fulfil at least one intended function; 
  3. ‘large-scale stationary industrial tools’ means a large-scale assembly of machines, equipment, and/or components, functioning together for a specific application, permanently installed and de-installed by professionals at a given place, and used and maintained by professionals in an industrial manufacturing facility or research and development facility; 
  4. ‘large-scale fixed installation’ means a large-scale combination of several types of apparatus and, where applicable, other devices, which are assembled and installed by professionals, intended to be used permanently in a pre-defined and dedicated location, and de-installed by professionals; 
  5. ‘cables’ means all cables with a rated voltage of less than 250 volts that serve as a connection or an extension to connect EEE to the electrical outlet or to connect two or more EEE to each other; [7]

The term “large-scale” is never defined in the directive. So what is “Large-scale” when it comes to machine tools? An explanation of the term is given in two places, [9] and [11]. The overall descriptions get a bit involved, but essentially it comes down to products that weigh 3 tons or more, or are at least 2.5 m x 2.5 m. Anything smaller than this is not considered “large-scale” and is therefore within the scope of the WEEE Directive. Some examples of “large-scale stationary industrial tools” include [9]:

  • Machines for the industrial production and processing of materials and goods, such as
    • CNC lathes;
    • Bridge-type milling and drilling machines;
    • Metal forming presses;
    • Newspaper printing presses;
  • Machines for the testing of work pieces, such as
    • Electron beam, laser, bright light, and deep ultra violet defect detection systems;
    • Automated integrated circuit board and printed wiring board testers;
  • Cranes;
  • Other machinery of similar size, complexity and weight.

What then, is a “large-scale fixed installation”? [9] can help us out here too. Some examples are given in the FAQ:

  • Production and processing lines, including robots and machine tools (industrial, food, print media etc.);
  • Passenger lifts;
  • Conveyor transport systems;
  • Automated storage systems;
  • Electrical distribution systems such as generators;
  • Railway signalling infrastructure;
  • Fixed installed cooling, air conditioning, and refrigerating systems or heating systems designed exclusively for non-residential use.

So, machine tools that weigh less than 3 tons, or are smaller than 2.5 x 2.5 m, are included in the scope of the RoHS directives, but machines larger that this, or systems that fit the descriptions of Large Scale Fixed Installations are out. What about WEEE? The WEEE Directive gives us some similar definitions in Article 3:

For the purposes of this Directive, the following definitions shall apply:

  1. ‘large-scale stationary industrial tools’ means a large size assembly of machines, equipment, and/or components, functioning together for a specific application, permanently installed and de-installed by professionals at a given place, and used and maintained by professionals in an industrial manufacturing facility or research and development facility;
  2. ‘large-scale fixed installation’ means a large-size combination of several types of apparatus and, where applicable, other devices, which: 
  3. are assembled, installed and de-installed by professionals; 
  4. are intended to be used permanently as part of a building or a structure at a pre-defined and dedicated location; and 
  5. can only be replaced by the same specifically designed equipment; 

WEEE also provides another list of products to consider in [8, Annexes I & II]. From the point of view of machine builders we need only look at Annex II, 6., which lists exclusions:

6. ELECTRICAL AND ELECTRONIC TOOLS (WITH THE EXCEPTION OF LARGE-SCALE STATIONARY INDUSTRIAL TOOLS)

  • Drills 
  • Saws 
  • Sewing machines 
  • Equipment for turning, milling, sanding, grinding, sawing, cutting, shearing, drilling, making holes, punching, folding, bending or similar processing of wood, metal and other materials 
  • Tools for riveting, nailing or screwing or removing rivets, nails, screws or similar uses 
  • Tools for welding, soldering or similar use 
  • Equipment for spraying, spreading, dispersing or other treatment of liquid or gaseous substances by other means 
  • Tools for mowing or other gardening activities 

If we take the interpretation of “large-scale” as [11], then it becomes clear that WEEE does not include most heavy machinery. Smaller equipment, i.e. not “large scale”, would be included. Seems clear enough, but how does this relate back to wire and cable?

In reading [9, Q5.2], we find that “Internal wires are not cables. Internal wiring in any EEE that is within the scope of RoHS 2 must simply meet the material restrictions like all other parts of the EEE; there is no individual CE marking and DoC requirement. If an EEE is subject to a transition period or a scope exclusion, the same applies to the internal wiring. The same principle applies to permanently attached cables, e.g. most lamp cables.” [9, Q5.3] continues this line of reasoning in relation to external cables, adding, “External cables that form part of another EEE because they are sold together or marketed/shipped for use with an EEE, e.g. power cords, must meet the material restrictions but do not need an individual CE marking and Declaration of Conformity if they are covered by the DoC for the EEE and the EEE is CE marked.” The comment regarding the applicability of the CE mark applies only to the RoHS Directive requirements.

Reading the definitions is never enough. The exclusions to the RoHS Directive [11, Art. 2] include some important points:

4. This Directive does not apply to:

c) equipment which is specifically designed, and is to be installed, as part of another type of equipment that is excluded or does not fall within the scope of this Directive, which can fulfil its function only if it is part of that equipment, and which can be replaced only by the same specifically designed equipment;
d) large-scale stationary industrial tools;
e) large-scale fixed installations;
j) equipment specifically designed solely for the purposes of research and development only made available on a business-to-business basis.

So machinery that is not either a large-scale stationary machine tool nor a large scale fixed installation is within the scope of the RoHS and WEEE Directives.

Summing Up

It looks like we have the full picture now, so let’s recap. Wire and cable products:

  • are included in the LVD, despite their usual classification as components, and therefore require CE Marking under this directive
  • are excluded from RoHS and WEEE when in component form,
  • are included in RoHS and WEEE when used in small-scale machinery (i.e., not large-scale stationary industrial tools or a large-scale fixed installation), consumer products, and medical devices that are not in-vitro or active implantable devices

So why are these products CE marked when in component form? The most obvious answer seems to be that some wire and cable products have been explicitly identified in the Commission Guidance on the Directive [5, Annex II]. Further, these products must always be incorporated into some other product, many of which are included in the scopes of LVD, RoHS and WEEE. In the case of the LVD, wire and cable products have a direct impact on the safety performance of many safety-critical assembles, like cord sets, so performance of the wire and cable product is essential to the safety of the end product.  It’s worth noting here that “cables” are included in the examples [5, Annex II], but “wire”, e.g., an individual insulated conductor, is not mentioned. This implies that wire does not need to be CE Marked as a component.

Is there a mandatory requirement for the use of CE Marked or marked wire and cable products? No. No more so that there is for any other component that may be selected for use in a CE Marked product. However, it is always recommended to use CE Marked components whenever they are available, as this reduces the likelihood of problems related to these products causing issues with the compliance of the final product.

Acknowledgements

I’d like to acknowledge the contributions of the following people to this article, and offer my thanks for their assistance. Some of those listed are members of the IEEE Product Safety Engineering Society, as well as members of the EMC-PSTC list:

Mr. Jon Cotman, Mr. Ted Eckert, Mr. John Gavilanes, Mr. Richard Robinson, Mr. Joshua Wiseman, Mr. John Woodgate.

References

[1] DIRECTIVE 2006/42/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 17 May 2006 on machinery, and amending Directive 95/16/EC. Brussels: European Commission. 2006.

[2] DIRECTIVE 2004/108/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 15 December 2004 on the approximation of the laws of the Member States relating to electromagnetic compatibility and repealing Directive 89/336/EEC. Brussels: European Commission. 2004.

[3] DIRECTIVE 2006/95/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 12 December 2006 on the harmonisation of the laws of Member States relating to electrical equipment designed for use within certain voltage limits. Brussels: European Commission. 2006.

[4] International Electrotechnical Commission (IEC). “Electropedia: The World’s Online Electrotechnical Vocabulary,”  electropedia.org. [Online]. Available: http://www.electropedia.org [Accessed: 2013-12-19].

[5] L. Montoya, Ed. Guidelines on the Application of Directive 2006/95/EC (Electrical Equipment Designed for Use Within Certain Voltage Limits). August 2007 (Last Modified: January 2012). Available: http://ec.europa.eu/DocsRoom/documents/8716/attachments/1/translations/en/renditions/native. [Accessed: 2015-08-24].

[6] DIRECTIVE 2002/95/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 27 January 2003 on the restriction of the use of certain hazardous substances in electrical and electronic equipment. Brussels: European Commission. 2002.

[7] DIRECTIVE 2012/19/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 4 July 2012 on waste electrical and electronic equipment (WEEE). Brussels: European Commission. 2012.

[8] DIRECTIVE 2011/65/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment. Brussels: European Commission. 2011.

[9] RoHS 2 FAQ. European Commission, Directorate-General Environment. 2012. Available: http://ec.europa.eu/environment/waste/rohs_eee/pdf/faq.pdf. Accessed 2013-12-12.

[10] DIRECTIVE 2011/65/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment, 2011/65/EU. European Commission, Brussels. 2011.

[11] DRAFT Frequently Asked Questions on Directive 2012/19/EU on Waste Electrical and Electronic Equipment (‘new WEEE Directive’). European Commission, Directorate-General Environment. Unpublished.

IMAGES: Selection of wire and cable products, unknown source. HAR mark courtesy Ören Kablo.