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A hazardous location (hazloc) is defined as an area where a potentially explosive gas or dust atmosphere may exist. In this article, we set out the requirements for hazardous location equipment for surface applications in the European Union (EU), and highlight some of the main differences and similarities between the ATEX system, the U.S. Hazloc system, and the international IECEx system for the certification of hazardous location equipment.

Mining applications have been excluded from this article. While mining applications do have many of the same requirements, mine-specific requirements also take into account the particular hazards associated with working underground.

The ATEX Directives
The EU’s ATEX product directive (94/9/EC) for equipment used in hazardous locations became mandatory in July 2003. It is a CE marking directive, and is sometimes referred to as the “ATEX Product Directive” or “ATEX 100.” The directive covers the different requirements applicable to mining (group I) and surface (group II) applications, and applies to electrical and mechanical equipment, including electric motors, compressors, diesel engines, lighting fittings, control and communications devices, and monitoring and detection equipment. For most categories, mandatory third party certification by an ATEX Notified Body is required. ATEX Notified Bodies are European organisations accredited by their national governments as competent to conduct ATEX assessments and issue Notified Body certificates.

A second ATEX directive (1999/92/EC) became mandatory in July 2006. It applies to the locations themselves and contains rules for the persons responsible for the location. This is sometimes referred to as the “ATEX Use Directive” or “ATEX 137.” As it is comparatively new, its impact is still reverberating through many parts of the European manufacturing industry.

The two directives are linked because the ATEX Use Directive not only defines the extent of the hazardous area (the zone), but also specifies the categories of ATEX equipment (according to 94/9/EC) that are permitted to be used in that zone. So it is important for manufacturers of equipment to understand both directives.

Applying the Directives
In order to provide consistency in the application of ATEX rules, the European Commission has a Standing Committee, comprising members from all EU countries, that is responsible for ATEX policy. In addition, the Notified Bodies operate a forum for discussing and addressing technical issues affecting compliance, known as the ExNB Group. The ExNB Group is independent, but has links to the Standing Committee.

Details of the output of the Standing Committee and the ExNB Group can be found on the EU Commission’s Europa website (http://ec.europa.eu/enterprise/atex/index_en.htm). In May 2007, the Commission produced a guidance document on the application of the ATEX product directive. This is also available for free download from the Europa website.

Hazardous Zones
A hazardous zone is determined according to the rules set out in EN 60079-10. ATEX recognizes three classes of zone for both gas and dust environments. Table 1 compares the ATEX and U.S. National Electrical Code 500 and 505 classifications.

Area classification Surface applications	EU ATEX			US NEC Article
	EU ATEX			500		505
	Gas	Dust	Permitted equipment	Gas	Dust	Gas
Flammable atmosphere is present continuously or for long period of time (often quantified as >1000hrs/yr)	Zone 0	Zone 20	Gas - 1G Dust - 1D	See note	See note	Class I, Zone 0
Flammable atmosphere is likely to occur during normal operation (often quantified as >10 and <1000hrs/yr)	Zone 1	Zone 21	Gas - 1G, 2G Dust - 1D, 2D	Class I, Div 1	Class II, Div 1	Class I, Zone 1
Flammable atmosphere is not likely to occur in normal operation (i.e. only rarely) and, if it occurs, will exist for only a short time (often quantified as <10hrs/yr)	Zone 2	Zone 22	Gas - 1G, 2G, 3G Dust - 1D, 2D, 3D	Class I, Div 2	Class II, Div 2	Class I, Zone 2
Note: There is no direct equivalent of a zone 0 or 20 in the US NEC Article 500 system.

Table 1: ATEX zoning and categories

It is worth noting that all of these classification systems sub-divide the gas groups and temperature classes within the gas classification. The U.S. and ATEX systems differ in that the ATEX system does not have dust groups (defining them instead by temperature classification alone), and the U.S. system defines its hazardous locations into two rather than three types (although there is some equivalence between the types).

ATEX Equipment Categories
For each zone classified, the level of protection required for equipment to be used in that zone is defined. Whereas the U.S. systems directly link equipment to location, the ATEX system divides equipment into three categories (1, 2 and 3), and only permits certain categories of equipment to be used in a given zone. Each ATEX category is further sub-divided into either gas (G) or dust (D) hazard protection (e.g., 2G, 1D).

A risk assessment approach for the acceptance of Ex equipment has been introduced by the IECEx within installation standard IEC 60079-14. This is an alternative method to the current prescriptive and relatively inflexible approach, which links equipment directly to zones within IECEx standards. Hence, the most recent IEC 60079-0 standard (5th edition, 2007) adopts the concept of equipment protection levels (EPL). These apply to gases (Ga, Gb and Gc) and dusts (Da, Db and Dc), and are equivalent to the ATEX Categories 1, 2 and 3. IEC 60079-0 (5th Ed) will be adopted as EN 60079-0 during 2008 and harmonised for ATEX purposes.

The ATEX Conformity Assessment Procedure
Once the required ATEX equipment category has been established, then the process of proving the safety of the equipment can begin. Depending on the category and technology, the manufacturer may be required to use an ATEX Notified Body to certify their equipment.

The certification process and the role of the Notified Body are defined by the conformity assessment procedures as set out in Annexes III to IX of the ATEX Product Directive (see Table 2). The conformity assessment procedures define the rules for ATEX compliance of a particular category of equipment. It should be noted that, where more than one category is present, the highest category defines the conformity assessment procedure for the whole equipment.

Category	Evaluation stage	Production control stage
1G or 1D Zone 0	Electrical or non-electrical equipment for series production - EC Type Examination by Notified Body (Annex III) leading to issue of an EC Type Examination Certificate	Either Production QA (Annex IV) – factory inspection by Notified Body (based on ISO9001) leading to issue of a Quality Assurance Notification
		Or Product verification (Annex V) – product test and inspection by Notified Body at factory leading to issue of a Quality Assurance Notification
	Electrical or non-electrical equipment for bespoke production - unit verification by Notified Body (Annex IX) of single sample only (no factory inspection required) leading to issue of a Unit Verification Certificate
2G or 2D Zone 1	Electrical equipment for series production - EC Type Examination by Notified Body (Annex III) leading to issue of an EC Type Examination Certificate	Either Conformity to type (Annex VI) – factory and test inspection by Notified Body leading to issue of a Quality Assurance Notification
		Or Product QA (Annex VII) – factory inspection by Notified Body (based on ISO9001) leading to issue of a Quality Assurance Notification
	Non-electrical equipment for series production	Internal Production Control by manufacturer (Annex VIII) and send the technical file to a Notified Body.
	Electrical or non-electrical equipment for bespoke production - unit verification by Notified Body (Annex IX) of single sample only (no factory inspection required) leading to issue of a Unit Verification Certificate
3G or 3D Zone 2 (see note)	Electrical or non-electrical equipment for series or bespoke production - test report produced by manufacturer or any competent person	Internal Production Control by manufacturer (Annex VIII)
	Option for electrical or non-electrical equipment for bespoke production - unit verification by Notified Body (Annex IX) of single sample only (no factory inspection required) leading to issue of a Unit Verification Certificate
Note: Category 3 equipment can be self certified by the manufacturer, although many purchasers may still prefer a third-party certification. Issue of an EC Type Examination Certificate or Quality Assurance Notification is not permitted for category 3 equipment.

Table 2: ATEX Conformity Assessment Annexes

Evaluating Equipment
All categories of ATEX equipment must be demonstrated as being safe. This is achieved through compliance with the essential health and safety requirements (EHSRs) listed in Annex II of the ATEX Product Directive. Whilst there is no legal requirement to apply one of the ATEX harmonised EN standards, this is the usual method used. These standards can provide a presumption of conformity with the EHSRs and hence are an easy way of proving compliance.

The latest set of ATEX standards are defined by the EN 60079 series for electrical equipment used in gas environments, the EN 61241 series for electrical equipment used in dust environments, and the EN 13463 series for mechanical equipment for use in either gas or dust environments.

The electrical standards are heavily based on the corresponding international IEC series; hence, compliance with ATEX can also provide a path to compliance outside of the European Union. Some of the newer UL and CSA hazardous area equipment standards are also based on the same common IEC 60079 documents (e.g., UL 60079-0). It is worth noting that many of the EN standards have recently been published or re-issued, and have replaced earlier series of ATEX standards (e.g., the old EN 500xx series).

Whilst existing equipment may still use the older series of standards for ATEX compliance, new equipment should comply with the latest EN standards. A list of the commonly used current EN standards is given in Table 3. A copy of the full list of standards is available in the ATEX section of the Europa web site. It should be noted that the EHSRs are the compliance benchmark; therefore more than one EN standard may be necessary for complex equipment.

Electrical (gas)

EN60079-0:2006* (IEC60079-0:2004) – General requirements for gases

EN60079-1:2004 (IEC60079-1:2003) – Flameproof equipment
for (Ex d)

EN60079-11:2007 (IEC60079-11:2006) – Intrinsic safety (Ex i)

Electrical (dust)

EN61241-0:2006* (IEC61241-0:2004) – General requirements for dust

EN61241-1:2004 (IEC61241-1:2004) – Protection by enclosures for dust (tD)

EN61241-11:2006 (IEC61241-11:2006) – Protection by intrinsic safety (iD)

Mechanical (gas and dust)

EN13463-1:2001 – General requirements

EN13463-5:2003 – Protection by construction (c)

EN13463-8:2003 – Protection by liquid immersion (k)

* Likely to be combined into a new EN60079-0 during 2008

Table 3: Examples of current ATEX standards

A Notified Body must be involved in the evaluation for all Category 1 equipment and Category 2 electrical equipment. The Notified Body will issue an EC Type Examination Certificate when a product for series production complies with the test and assessment requirements of Annex III. This Certificate is evidence that the design complies with the applicable technical requirements, and applies to any equipment manufactured under one of an appropriate Quality Assurance Notification (or production licence).

For bespoke (i.e., customized) equipment, the Notified Body may issue a certificate under Annex IX specific to the sample that they inspected. This certificate is called a Unit Verification Certificate and may be used for all categories of equipment.

Where the evaluation process is standards-based, it follows a route that will be familiar to manufacturers of hazloc equipment. However, the EN/IEC standards do contain sufficient differences in requirements to U.S. national standards, such as UL 913 and UL 1604, that difficulties may be encountered if the equipment has not been designed with the EN/IEC standard in mind.

As part of the evaluation process the manufacturer should compile a technical documentation file as described in Annex III, VIII or IX. In general, this file contains:

A general type-description;
Design and manufacturing drawings and layouts of components, subassemblies, circuits, etc;
Descriptions and explanations necessary for the understanding of said drawings and layouts and the operation of the product;
A list of the harmonized standards, applied in full or in part, and descriptions of the solutions adopted to meet the essential requirements of the directive where harmonized standards have not been applied;
Results of design calculations made, examinations carried out, etc;
Test reports.

Establishing Effective ATEX Production Control
The production control (or factory inspection) stage ensures continued conformity. A Notified Body must be involved in this stage for all Category 1 and Category 2 equipment.

The Notified Body will issue a Quality Assurance Notification when a product complies with the requirements of one of the Annexes IV, V, VI or VII.

The production control Annexes are divided into two types, which correspond to equipment categories. Annexes IV and VII are based on established quality assurance principles and use standard EN 13980:2002 in conjunction with the ISO 9001:2000 standard in order to determine compliance. Inspections for these Annexes are generally conducted twice every three years.

Annex VI uses similar principles as those applied for U.S. Hazloc inspections, but these inspections are conducted annually. Annex V is a rarely used procedure because it relies upon witnessed tests of every production sample by the Notified Body.

Where EN 13980 is used, manufacturers usually need to make minor modifications to their quality system documentation in order to comply with the specific requirements of the standard. Due to the relative infrequency of inspections when compared to the U.S. Hazloc system, the quality of the ISO 9001 system and the associated internal audit process are particularly important. However, the requirements of EN 13980 have some equivalence to Hazloc requirements (e.g., purchasing documentation and stock control) and hence should not present significant problems to manufacturers who are familiar with the U.S. approach. The IECEx certification system also includes a factory inspection element which is very similar to EN 13980.

Applying ATEX Marking
The ATEX Product Directive outlines mandatory marking for all ATEX products, which includes the distinctive Ex symbol followed by the group designation, the equipment category and area of use. For example, a II 2 G marking shows suitability for zone 1, gas, surface applications.

In addition to this marking from the directive, there are additional items derived from the EN/IEC standards. These indicate the protection concept used, the temperature class and other pertinent data. For example, Ex ib IIC T4 shows intrinsic safety has been applied covering a IIC gas group with a maximum temperature of 135ºC. The full marking from these two examples would thus be:

II 2 G Ex ib IIC T4

It would also be necessary to show the EC Type Certificate number (e.g., TRL08ATEX00000X) and the CE mark followed by the number of the Notified Body responsible for the Quality Assurance Notification.

The ATEX Declaration of Conformity
The ATEX Product Directive has quite specific requirements for the content of the EC Declaration of Conformity. Some of this content is different from other CE marking directives (e.g., the EMC Directive, the Low Voltage Directive). Whilst the exact layout of the ATEX Declaration of Conformity is not prescribed within the directive, the mandatory content is prescribed in Annex X as explained in Table 4.

Requirement	Explanation
a) Name or identification mark and the address of the manufacturer or his authorised representative in the Community.	Note that the name on the product places the named organisation in the position of manufacturer (or authorised representative).
b) A description of the equipment, etc. A descriptive product designation, e.g. Motor Control Unit Type ABC 123, and its intended use.	For an assembly it should list the items in the assembly that are ATEX equipment in their own right, and which have been separately assessed.
c) All relevant provisions fulfilled by the equipment, etc.	The marking included on the product e.g. II 2 G Ex ib IIC T4.
d) Where appropriate, the name, identification number and address of the notified body and the number of the EC-type examination certificate.	Name and number of the notified body (or bodies) conducting the EC-type examination. In the case of category 2 non-electrical equipment, it should refer to the Notified Body holding the copy of the technical documentation file. Where relevant, if the body responsible for oversight of the QA regime is not the same as the one issuing the original certificate, it should be named separately. However, the name and address of a Notified Body involved in the production phase is not a mandatory requirement. Where the Annex applied for conformity assessment does not require the use of a Notified Body then this section is not appropriate.
e) Where appropriate, reference to the harmonized standards.	The harmonized standards quoted in the technical documentation file should be listed here. Harmonized standards are those listed in the Official Journal of the European Union. The harmonized status of standards may change over time. When standards are removed from this list (e.g. when they have been withdrawn or superseded) then they cease to be harmonized and should be listed under section (f) of the declaration.
f) Where appropriate, the standards and technical specifications used.	Other standards (e.g. non-harmonized) and technical specifications used for confirming compliance with the essential health and safety requirements of the directive (Annex II) and quoted in the technical documentation file should be listed here. Where only harmonised standards have been applied then this section is not appropriate. However, note that the harmonized status of standards may change over time.
g) Where appropriate, references to other Community Directives which have been applied.	If this is a multi-directive declaration, it should already be clear from the heading to which directives the product conforms.
h) Identification of the signatory who has been empowered to enter into commitments on behalf of the manufacturer, etc.	The signatory needs to be a responsible officer of the manufacturer or of the authorised representative.

Table 4: Content of ATEX declaration of conformity

Conclusion
The process for ATEX certification has similarities to both the U.S. and IEC systems in that they all involve evaluation of a sample of product and follow-up factory inspections. The specific requirements are outlined in EN published standards, many of which are based on IEC standards. Whilst these standards, for the present, differ from U.S. standards, there are many common areas. If attention is paid to the differences, then compliance with ATEX should pose few problems for U.S. manufacturers. n

Simon Barrowcliff is the Director responsible for the ATEX business at TRL Compliance Ltd (www.trac-trl.com), a UK ATEX Notified Body. He can be reached at simon.barrowcliff@trac-trl.com.