Intrinsically safe certification and the ATEX Directive
June 1st 2007

Companies across all industry sectors put the health and safety of their workers as a priority but any industry working in potentially explosive atmospheres have even greater safety concerns explains Casella's Gary Noakes

The ATEX Directive (94/9/EC), forces all EU Member States to design, produce and manufacture products for use in potentially explosive atmospheres within certain technical and legal requirements. The Directive covers electrical and mechanical equipment and protective systems, which may be used in potentially explosive atmospheres (flammable gases, vapours or dusts.) According to the Directive, the term 'equipment' is defined as 'any item which contains a potential ignition source and which requires special measures to be incorporated in its design and/or its installation in order to prevent the ignition source from initiating an explosion in the surrounding atmosphere.' Products are required to be categorised by the level of protection that they offer against the risk of them becoming a potential source of ignition in an explosive atmosphere.

The gas groupings and the temperature codes are reflected in the markings that appear on electrical equipment, which has been certified for use in a hazardous area. The marking of the gas grouping and temperature code helps the user to identify the type of explosive atmosphere in which it can be safely installed.

Hazardous zones Hazardous areas are further divided into zones. These zones relate to the predicted occurrence of when an explosive atmosphere may be present in the area. Zones are defined as being: ZONE 0, where an explosive atmosphere is continuously present, or present for long periods ZONE 1, where an explosive atmosphere is likely to occur in normal operation ZONE 2, where an explosive atmosphere is not likely to occur in normal operation and if it does occur it will exist only for a short time.

The ATEX requires the categorisation of each part of a hazardous process as Zone 0,1 or 2, according to the risk of an explosion occurring.

Equipment group I (mining) M1 – High integrity of protection for mining equipment.

Two fault conditions M2 – Reliability concept of protection for mining equipment Equipment group II (non-mining) CAT 1 (Zone 0) – Still safe with two faults CAT 2 (Zone 1) – Increased safety under abnormal operating conditions CAT 3 (Zone 2) – Equipment which is appropriate in normal operating conditions The marking of the equipment with the category will help the end-user with their selection in that it identifies which Zone the equipment can be safely installed. This is a major improvement over the old cryptic marking system that only listed the protection concepts used in the design of the equipment. For example, a previous classification might have been: EEx ia IIC T4 for ATEX would be Ex II 1 G. This meant that the user of the equipment had to be familiar with all eight recognised protection concepts and had to know which of them was suitable for a particular type of Zone.

Casella has been supplying hand held monitoring equipment for air, dust and noise sampling for many decades but until recently, no products were ATEX approved. Prior to achieving ATEX (and UL) approval, none of the products could be targeted to users who had zoned intrinsically safe areas. This precluded sales to petrochemical plants, oil refineries, offshore rigs, and many other chemical, textiles, mining applications. It was estimated that more than 35% of the potential market for these products was therefore unobtainable without the correct certification. Prior to this time, users could use the equipment in zoned areas, but only by issuing "hot-work" permits, which was laborious and time consuming process.

ATEX approved products Over the past few years, a range of products have now been put forward for and received ATEX certification. These include: Apex Personal Air Sampling Pumps – these are used to take air samples on an operator, onto a filter media for gravimetric and other chemical analysis, to ensure compliance with the COSHH legislation.

Voc Pro – a hand held PID (photoionization detector) for the detection of organic solvents and vapours (VOC's) Microdust 880 – a portable real time aerosol/dust monitor for assessing concentrations of suspended particulate matter. It is ideal for walk through surveys, and data can be downloaded and analysed via graphical software.

dBadge – this is a small cable free personal noise dosimeter device which can measure all occupational noise parameters in potentially explosive atmospheres, as well as the time history on an individuals exposure throughout the day.

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