ATEX directive

The ATEX directive is two EU directives describing what equipment and work environment is allowed in an environment with an explosive atmosphere.

Directives

As of July 2006, organisations in EU must follow the directives to protect employees from explosion risk in areas with a explosive atmospheres.

There are two ATEX directives (one for the manufacturer and one for the user of the euipment):
* the ATEX 95 "equipment" directive 94/9/EC, Equipment and protective systems intended for use in potentially explosive atmospheres;
* the ATEX 137 "workplace" directive 99/92/EC, Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.ATEX gets its name from the French title of the 94/9/EC directive: "Appareils destinés à être utilisés en ATmosphères EXplosibles"

Employers must classify areas where hazardous explosive atmospheres may occur into zones. The classification given to a particular zone, and its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does.

Areas classified into zones (0,1,2 for gas-vapor-mist and 20,21,22 for dust) must be protected from effective sources of ignition. Equipment and protective systems intended to be used in zoned areas must meet the requirements of the directive. Zone 0 and 20 required category 1 marked equipment, zone 1 and 21 required category 2 marked equipment and zone 2 and 22 required category 3.3 marked equipment. Zone 0 and 20 are the most dangerous.

Equipment in use before July 2003 is allowed to be used indefinitely provided a risk assessment shows it is safe to do so.

The aim of directive 94/9/EC is to allow the free trade of ‘ATEX’ equipment and protective systems within the EU by removing the need for separate testing and documentation for each member state.

The regulations apply to all equipment intended for use in explosive atmospheres, whether electrical or mechanical, including protective systems. There are two categories of equipment I for coal mining and II for industrial applications. Manufacturers who apply its provisions and affix the CE marking and the Ex marking are able to sell their equipment anywhere within the European union without any further requirements being applied with respect to the risks covered being applied. The directive covers a large range of equipment, potentially including equipment used on fixed offshore platforms, in petrochemical plants, mines, flour mills and other areas where a potentially explosive atmosphere may be present.

In very broad terms, there are three pre-conditions for the directive to apply: the equipment a) must have its own effective source of ignition; b) be intended for use in a potentially explosive atmosphere (air mixtures); and c) be under normal atmospheric conditions.

The directive also covers components essential for the safe use and safety devices directly contributing to the safe use of the equipment in scope. These latter devices may be outside the potentially explosive environment.

Manufacturers/suppliers (or importers, if the manufacturers are outside the EU) must ensure that their products meet essential health and safety requirements and undergo appropriate conformity procedures. This usually involves testing and certification by a ‘third-party’ certification body (known as a Notified Body e.g. Lloyd's, TUV) but manufacturers/suppliers can ‘self-certify’ category 3.3 equipment (technical dossier including drawings, hazard analysis and users manual in the local language) intended to be used in less hazardous explosive atmospheres. Once certified, the equipment is marked by the ‘CE’ and ‘Ex’ symbol to identify it as such. The technical dossier must be kept for a period of 10 years.

Certification ensures that the equipment or protective system is fit for its intended purpose and that adequate information is supplied with it to ensure that it can be used safely.

Technical definitions

;Effective ignition source

Effective ignition source is a term defined in the European ATEX directive as an event which, in combination with sufficient oxygen and fuel in gas, mist, vapor or dust form, can cause an explosion. Methane, hydrogen or coal dust are examples of possible fuels. [Michelis, J.: „Explosionsschutz im Bergbau unter Tage“, Verlag Glückauf Essen, 1998, ISBN 3-7739-0900-4]

Effective Ignition Sources are:
* Thunder strikes.
* Open flames. This varies from a lit cigarette to welding activity.
* Mechanically generated impact sparks. For example, a hammer blow on a rusty steel surface or a hammer blow on a flint stone.
* Mechanically generated friction sparks. The combination of materials and speed determine the effectiveness of the ignition source. For example 4.5 m/s steel-steel friction with a force greater than 2 kN is an effective ignition source. The combination of aluminum and rust is also notoriously dangerous. More than one red hot spark is often necessary in order to have an effective ignition source, however. [See Explosionsschutz im Bergbau unter Tage page 92] .
* Electric sparks. For example a bad electrical connection or a faulty pressure transmitter. The electric energy content of the spark determines the effectiveness of the ignition source.
* High surface temperature. This can be the result of mechanical friction in a stuffing box or bearing, or of a high temperature liquid pumped into a vessel resulting in a hot vessel surface.
* Electrostatic discharge. This can be caused by air sliding over a wing, or non-conductive liquid flowing through a filter screen.
* Radiation.
* Adiabatic compression. Air is pumped into a vessel and the vessel surface heats up.

External links

* [http://ec.europa.eu/enterprise/atex/index_en.htm ATEX euronorm]
* [http://ec.europa.eu/enterprise/atex/direct/text94-9-en.pdf Directive 94/9/EC]
* [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2000:023:0057:0064:EN:PDF Directive 1999/92/EC]
* [http://ec.europa.eu/enterprise/atex/guide/atexguidelines_august2008.pdf ATEX Guidelines (Second Edition - July 2005) - Updated August 2008]