Area classification in the context of electrical safety in hazardous environments is a critical framework used to categorise areas where explosive or flammable gases, vapours, dusts, or fibers may be present. This classification helps in specifying the types and designs of equipment that can safely be used in such areas. The classifications are broadly divided into three categories: Class, Group, and Division. Let’s explore each category:

Class

The “Class” designation identifies the types of hazardous substances that are predominant in the atmosphere.

  • Class I: Locations where flammable gases or vapours are present in the air in sufficient quantities to be explosive or ignitable.
  • Class II: Locations where combustible dust may be found in the air in quantities sufficient to be explosive or ignitable.
  • Class III: Locations where ignitable fibres or flying’s are present, but not likely to be in the air in sufficient quantities to produce ignitable mixtures.

Group

The “Group” designation is used to further classify the exact nature of the hazardous substances in the environment based on their explosive or ignition properties. It typically pertains to the chemical characteristics of the substances.

  • Group A: Acetylene, which is a gas with extremely high flame propagation properties.
  • Group B: Hydrogen, butadiene, ethylene oxide, propylene oxide, and acrolein, which have significant explosive capabilities.
  • Group C: Ethyl ether, ethylene, and similar gases.
  • Group D: Propane, butane, methane, gasoline, naphtha, benzene, butyl alcohol, ammonia, and similar gases.
  • Group E: Metal dust, such as aluminium and magnesium.
  • Group F: Carbonaceous dusts, including coal, carbon black, charcoal, and coke dust.
  • Group G: Dusts not included in E and F, such as flour, starch, grain, wood, plastic, and chemicals.

Division

The “Division” designation refers to the likelihood of the hazardous material being present in an ignitable concentration.

  • Division 1: Where ignitable concentrations of hazards exist under normal operation conditions or where hazard is often released during regular operation or maintenance.
  • Division 2: Locations where the ignitable substances are not likely to be present in an atmosphere under normal operating conditions.

Unclassified or Non-hazardous Areas

Areas that do not qualify under any of these classifications are deemed unclassified or non-hazardous. These areas are considered safe from the risks associated with explosive or ignitable concentrations of hazardous elements.
This structured classification system allows for proper selection and installation of electrical equipment according to the specific risks associated with each area, ensuring safety and compliance with regulatory standards.