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What is a Hazardous Area Classification ?

A Hazardous Area classification is a method of analysing and classifying the environment where explosive atmospheres could occur to allow electrical workers to select equipment appropriate for the area. A hazardous area classification is a detailed engineering assessment that looks at a range of factors that will influence the size and extent of a site hazardous area. The hazardous area classification assesses the following

  • Likelihood and duration of the explosive atmosphere
  • Ignition temperature of the gas and vapour
  • Upper and lower explosive limits of the gas or vapour
  • Ignition Energy of the gas or vapour
  • Relative density of the gas

In Australia the responsibility for having an area classification completed rests with the persons or parties in control of the installation. These people will often contact specialist firms to complete the classification on their behalf as it is specialised engineering task.

The hazardous area classification in flammable gas and vapour atmospheres (Group II) and combustible dust atmospheres Group III is vital for electrical workers. The hazardous area classification defines the hazardous areas extent and the properties of the gas, vapour or combustible dusts concerned. Without a classification it is not possible to select electrical equipment or to decide on the required installation practices.

There are normally 3 parts to a classification, the material schedule, the source of releases document and the hazardous area zone map.

Material Schedule: The material schedule is a detailed list of the combustible dusts, chemicals, liquids and gases contained on site. This schedule will detail the individual properties of the combustible dusts, liquids and gases and contains vital information for assessing the risks posed by these materials like the ignition temperature, the gas/dust group, vapour density, explosive limits.

Source of Release Schedule: Once the combustible dusts, flammable gases and liquids have been identified the classification team will look at the facility and look for ‘sources of release’. A source of release is a point or location from which a dust, gas, vapour, mist or liquid may be released into the atmosphere so that an explosive gas atmosphere could be formed. Common sources of release include tanks, valves, pipe flanges, pressure safety valves. Once the sources of release are identified they are documented in a source of release table.

Zone Maps: Once the material schedule and the source of release schedule are completed a final classification zone map can be drawn up, the classification zone map is a graphical and illustrative representation of the sources of release and material schedule.

If you need any further details, contact Lithium Oil and Gas for information and guidance on your specific installation requirements.


“This following information represents and opinion only of a general nature, the specifics of each individual situation must be taken into account with reference to the relevant Legislation, Codes of practice and Australian standards. Professional advice should be sort if there is any doubt.”

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