The EU ATEX directieven
The relevant directives of the EU are:
? 94/9/EC Equipment and protective systems intended for use in potentially explosive atmospheres.
? 99/92/EC Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.
The directives are adopted into national law by the individual member states. Some candidate entrant states have also aligned their national regulations with ATEX.
ATEX covers hazards arising from the use of both electrical and mechanical equipment in potentially explosive atmospheres. The ATEX equipment directive and the accompanying health and safety directive, specifying the protection of workers, apply to the European Union and are in operation from July 2003. The safety directive requires hazardous areas to be subjected to a risk analysis, classified into Zones and suitably equipped.
The manufacturer must make a declaration of compliance with the equipment directive and apply the CE mark before the product can be placed on the market in the EU. The individual governments of the member states appoint ?notified bodies? to carry out testing and certification. Apparatus is divided into Equipment Groups (I for mining and II non-mining), the ignitable component of the explosive atmosphere, Gas (G) and Dust (D) and Categories 1, 2 and 3. The Categories provide respectively, very high, high and normal levels of protection against ignition. The Categories should be considered as achieving the level of protection obtained by applying the existing protection techniques (Ex d, Ex e etc). Alternatively, the existing techniques can be replaced or supplemented by new concepts and engineering judgements made by the manufacturers in the design and construction of the apparatus. Where required, this would be validated by notified bodies performing an EC type examination of the product.

In practice, the Categories are equated to suitability for Zones. The actual category of apparatus specified by the user for a Zone will depend on the overall risk assessment. The Zoning considers only the probability of the occurrence of an explosive atmosphere, its extent and duration. It does not consider the consequential effects of an ignition having taken place or of the environment. Apparatus will be marked with the Grouping and Category in addition to the marking required by the individual protection standards.
The Chalmit range of products falls within Group II for industrial applications and covers designation as Category 2 or 3. This means that products will generally be suitable for use in Zone 1 and 2 areas as defined by the codes of practice for zoning such as EN 60079-10 (IEC 60079-10) and selection, EN 60079-14 (IEC 60079-14) etc.
Currently EN 60079-14 does not refer to categories so the protection code of the apparatus is used as listed in the standard or the category can be equated as being suitable for a specific Zone as detailed in the directive. These codes of practice provide the user with guidance in selecting apparatus needed to obtain the degree of safety that is required for the particular hazardous area application.

The Euro-normes (EN) have been updated for ATEX but as the updating mainly consisted of a cross reference to the ATEX categories this did not affect the standards technically except where co-incidental technical amendments were made. Compliance with the Euro-norme gives a presumption of compliance with those aspects of the directive covered by the standard. These are ?The Essential Health and Safety Requirements? EHSR?s. Lists of standards giving a presumption of compliance with the directive are published in the official journal (OJ) of the EU. The European Commission web site contains a large quantity of material concerning the directives along with the actual directive itself and the guidelines for its application.

An EC type examination by a notified body is mandatory for Category 1 and 2 electrical equipment but not for Category 3. Chalmit have chosen to obtain a certificate of compliance from a third party for Category 3 equipment in order to promote customer confidence and continue the long standing practice that Chalmit has used for Ex N apparatus. The designation EC can not be used for certification of Category 3 apparatus. In the data. the term ?type examination? rather than ?EC type examination? is used for Category 3 apparatus.

The relationship between Categories and applications is shown in Table 4.

Marking of ATEX product and CE mark

The product carries the ATEX marking which includes the CE mark, the Group, the Category and the Category sub-group G or D. The product also carries the normal coding, Ex d etc. and the surface temperature and ambient temperature (Tamb) ratings. The Group also forms part of the marking in the product standards and pre-dates ATEX. The Category is additional to the previous marking. This means that all of the familiar marking is still present.
All products carry the general product safety and electromagnetic compatibility CE mark on the product, installation manual or packaging, as appropriate. The marking attests that the product meets the requirements of the Low Voltage and Electro-Magnetic Compatibility (EMC) directives of the EU as transposed into UK law. If the product carries the CE mark for ATEX it is not repeated. The scope of compliance is given in the IOM.
Products exported directly outside of the European Community are not required to carry any CE marking but local marking regulations may apply.
Gas Group

Surface temperature rating and gas grouping
Any explosive mixture can be classified for explosion protection under two main characteristics, temperature of ignition by a hot surface and the spark energy to ignite it. The spark energy of ignition is also related to the intensity of the explosion. This latter property is crucial to the design of the joints in flameproof enclosures (Ex d) and the energy level limit of intrinsically safe (Ex i) and energy limited circuits. Other important subsidiary characteristics are the specific gravity and flash point, which are used in the determination of the area classification.

Surface temperature for ignition of gas
The surface temperature rating is measured in the most onerous design attitude at the most severe supply voltage condition within the design tolerance. Usually this is +10% of rated voltage for lighting and with any fault or overload condition which could normally occur in service. A normal overload condition for motors is the starting or stalled condition and, for luminaires, the end of life of a lamp. In the case of Ex d, Ex m, Ex q and also restricted breathing Ex nR and dust proof enclosure methods, the maximum temperature is measured on the external surface. In other methods of protection the maximum internal temperature of the apparatus is measured.

The explosive mixtures are allocated into broad bands giving the Temperature Classes shown in Table 5  

 
For dust protection using the enclosure methods the surface temperature is limited to a given value in ºC, the T grouping is not used.
Gas Group
The gas and vapour mixtures are classified as shown in Table 6. The possible number of chemical compounds is very extensive and the list shown is only representative. The classification shown is that associated with the IEC and CENELEC harmonised standards. The apparatus sub-groupings, A, B and C are only applicable to the design and marking of flameproof, intrinsically safe, energy limited and non incentive apparatus.

Protection against the ignition of explosive atmospheres formed from ignitable dust
In this catalogue are products for use with ignitable dusts.  Explosives dusts i.e. those not requiring the presence of air to ignite are outside the scope of ignitable dust protection.

With respect to the formation of an explosive atmosphere, the nature of dust is very different to that of gas or vapour. Dust, unlike gas does not disperse, it remains until cleared away by manual means or ventilation and can form layers. Layers of dust can ignite at much lower temperatures than clouds. This is because layers can insulate and increase the temperature and also because layers of some dust are prone to spontaneous combustion. The ignition of layers results in burning which can subsequently translate into an explosion. Layers have the potential to be disturbed and form clouds. Ignition data for dusts is given for clouds and layers. Typically, dust in a cloud form is harder to ignite than gas either by a hot surface or a spark. The maximum allowable surface temperature for apparatus present in dust clouds is de-rated from the actual surface temperature of ignition of the dust. The allowable surface temperature for layers is subject to further de-rating where layers exceed 5mm thick and extra heavy layers require special laboratory investigation by the specifier or user.
When installing floodlights, care must be taken to ensure that the face of the glass is positioned at such an angle that dust can not settle.
Ignitable atmospheres caused by dust may be prevented from arising by ventilation, containment and by good housekeeping. The area classification for dust is similar to that for gas, namely, Zone 20, Zone 21 and Zone 22, depending on the likelihood of a hazardous dust atmosphere being present. As a generality, the zones are smaller than those for gas. Equipment may be marked as suitable for both gas and dust hazards. If the apparatus carries marking for both dust and gas this does not mean both at the same time. The simultaneous presence of ignitable dust and gas is subject to special consideration and its potential for ignition must be investigated by a qualified person.

The dust ignition protection method for products in this catalogue is by enclosure to
IP6X or IP5X as appropriate. IP6X is required for ATEX Category 1 and 2 and for conducting dusts in any Category. Conducting dust ingress can cause incendive insulation failure. IP5X is a minimum for Category 3. The surface temperature is limited to a given value in ºC and the T grouping is not used. Currently the most recent enclosure standard is EN 50281-1-1 and is used for Chalmit apparatus to ATEX. The selection standard is EN 50281-1-2. and the area classification standard EN 50281-3.

It should be noted that the dust protection methods for the EU after ATEX comes into force are not identical with those of the rest of the world. The reference standards are set by the user and may be EN, IEC or a USA standard. Chalmit apparatus will generally comply with the
IEC 61241 series of standards for Practice A. The user must specify to which standard the product is required to comply. The standards are under further development and significant changes will take place during the period when this catalogue is current.

Reference is also made in this catalogue to products for use in NEC Class II and Class III locations. NEC dust protected products are to UL 844. The construction and testing is different to that specified in the Euro-norme but is very similar to the alternative Practice B given in the IEC standard. The main differences are gasket dimensions, thermal testing with a layer of dust and ingress testing using a heating and cooling cyling method.