HAZARDOUS AREA CLASSIFICATION

Description
. The information provided in this document is for educational purposes.
Hazardous areas are defined in DSEAR as "any place in which an explosive atmosphere may occur in quantities such as to require special precautions to protect the safety of workers".
The document provides an overview for the design and use of equipment used within potentially explosive atmospheres created by gases, vapours and ignitable dusts or fibres, commonly referred to as hazardous area zones.
Typically this includes such installations as oil/gas rigs, processing refineries, chemical production facilities, flammable liquids storage facilities, fuel transportation, petrol stations, paint production, paper production etc, however this list is not exhaustive and many new areas may be re-classified as hazardous. A “hazardous area” is defined as an area in which the atmosphere contains, or may contain in sufficient quantities, flammable or explosive gases, dusts or vapours. In such an atmosphere a fire or explosion is possible when three basic conditions are met. This is often referred to as the “hazardous area” or “combustion” triangle.
In order to protect installations from a potential explosion a method of analysing and classifying a potentially hazardous area is required. The purpose of this is to ensure the correct selection and installation of equipment to ultimately prevent an explosion and to ensure safety of life. The methods used to classify an installation can vary depending upon which part of the world it is located, but generally there are two main types of classification. In countries that have adopted the IEC (International Electrotechnical Commission) philosophy this is referred to as Zoning whilst in North American installations are classified by Classes, Divisions and Groups to ascertain the level of safety required.