Hazardous area classification is a common approach to controlling risk in working environments which may be prone to explosions due to the present of gas, vapour, dust, fibres or other atmospheric hazards.
In the UK, Hazardous Area Classification is governed by British Standard EN 60079/10.
There are also US Standards for area classification under OSHA as well as international standards under the International Electro-technical Commission (IEC).
In the UK, hazardous areas are defined in Dangerous Substances and Explosive Atmospheres Regulations (DSEAR, 2002) as "any place in which an explosive atmosphere may occur in quantities such as to require special precautions to protect the safety of workers".
In identifying the "special precautions" required, hazardous area classification is the method used to analyze and classify the environment where explosive atmospheres may occur.
The objective of hazardous area classification is to ensure the selection and installation of appropriate "intrinsically safe" plant and equipment to be used safely in the location, taking account of the properties of the hazardous substances that may be present.
In the UK context, the DSEAR extends the original scope of hazardous area classification from electrical sources of ignition, to now include nonelectrical sources of ignition, and mobile equipment that creates an ignition risk.
Hazardous areas are classified into zones based on an assessment of the frequency of the occurrence and duration of an explosive gas atmosphere, as follows:
Zone 0: Areas where an explosive atmosphere is present continuously or for long periods;
Zone 1: Areas where an explosive atmosphere is likely to occur in normal operation;
Zone 2: Areas where an explosive atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time; and
Safe Zone: Any area not expected to contain a hazardous atmosphere (e.g., homes).
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