A hazardous area is defined as an area in which an explosive atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of potential ignition sources.
Major industries affected would include oil, gas, petroleum refineries, chemical plants, sewerage treatment and grain handling. Other industries include spray painting shops, aircraft hangars, petrol depots, terminal and garages.
Therefore the use of any electrical apparatus in these areas is strictly controlled through various protection techniques to enable the operators to facilitate the handling or processing of the hazardous materials. This removes the possibility of ignition being caused by the electrical apparatus contained within hazardous area
The International Electrotechnical – Commission (IEC) have developed the IEC 60079 set of standards specific for Electrical equipment in explosive Gas and Dust atmospheres. These standards define the Protection Techniques in preventing electrical equipment creating a possible ignition source in a hazardous environment.
In having the IECEx Scheme in place it allows products to be tested and evaluated under these standards in being issued an IECEx certificate of conformity. Under the IECEx scheme the manufacturing of such certified equipment is audited by the accredited IEC bodies to ensure the quality systems and processes are in place to ensure compliance. After issuing the manufacturer with an IECEx QAR, ongoing surveillance audits are conducted annually to ensure such quality is maintained.
The IECEx standards have been adopted by Australia and the ANZEx Scheme is in-line with the IECEx Scheme. Therefore IECEx certificates are accepted into the ANZEx scheme for use in Australian installations. The European Directive 94/9/EC – ATEX follows the CENELEC EN standards that are generally now harmonised with the IEC standards. There may be some small differences as the standards are harmonise across all the hazardous area, installation and protection techniques standards.
It should be noted that under the ANZEx Scheme, unless ATEX equipment has had a Conformity Assessment conducted, it is not accepted for installation within Australia.
Conditions Required For An Explosion :
An explosion will only occur when three basic conditions are present: 1) Explosive material 2) Oxygen/Air 3) Sources of ignition
Air Sources of ignition Remove any one of these basic conditions and an explosion will not occur.