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, terminals 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 the hazardous area. 

Standards Australia prepares, publishes and maintains Australian Standards and in the case of hazardous areas, looks at all aspects of implementing standards that affect the certification, testing, installation and maintenance of electrical equipment in these areas. 

Note: Australian Standards has endorsed the adoption of the IEC 60079 gases and vapours and IEC 61241 dust series of standards as joint Australian / New Zealand Standards. In the new series of standards there is no reference to Class I and Class II areas. The different zones are identified as zones 0, 1 and 2 for explosive gas atmospheres and zones 20, 21 and 22 for explosive dust atmospheres.

Conditions required for an explosion

An explosion will only occur when three basic conditions are present:

• Explosive material
• Oxygen / air
• Sources of ignition

Remove any one of these basic conditions and an explosion will not occur.

 

Classification of hazardous areas

GROUP II Flammable gas, vapour or mist combustible dusts