Hazardous Area Classification – HAC

Definition of Hazardous Area and Hazardous Area Classification Zoning

When electrical equipment is used in, around, or near an atmosphere that has flammable gases or vapours, flammable liquids, combustible dust, ignitable fibers, or flyings, there is always a possibility or risk that a fire or explosion might occur.

Those areas where the possibility or risk of fire or explosion might occur due to an explosive atmosphere and/or mixture is often called a hazardous (or classified) location/area.

Hazardous areas can be defined 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 this context, ‘special precautions’ are best taken as relating to the construction, installation, and use of apparatus.

Area classification is a method of analysing and classifying the environment where explosive gas atmospheres may occur. The main purpose is to facilitate the proper selection and installation of the apparatus to be used safely in that environment, taking into account the properties of the flammable materials that will be present.

It is also important to take into account non-electrical sources of ignition, and mobile equipment that creates an ignition risk.

Hazardous Area Classification – Zones

Hazardous Area Classification Guides classify different zones based on an assessment of the frequency of the occurrence and duration of an explosive gas atmosphere, as follows:

— Zone 0: An area in which an explosive gas atmosphere is present continuously or for long periods;
— Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation;
— Zone 2: An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time.

The Zone defines the probability of the hazardous material, gas, or dust, being present in such a quantity that it may produce explosive or ignitable mixtures.

When the hazardous areas of a plant have been classified as per Hazardous Area Classification Guide and standards, the remainder will be defined as non-hazardous, sometimes referred to as ‘safe areas’.

Hazardous Area Classification – Class/Division

Note: In general, there are two systems used to classify hazardous areas.

— Class/Division system and
— Zone system

The Class/Division system is used predominantly in the United States and Canada, whereas the rest of the world generally uses the Zone system. However, the Zone System is more prevalent globally. Explore more on zoning systems at the HSE UK website and the Class system at the OSHA website.

Consultivo, being one of the practicing Hazardous Area Classification Consultants in India provides review, assessment & consulting services globally.

Practical considerations while conducting hazardous area classification

It’s important to consider the following points while conducting studies on the classification of hazardous areas:

— To know the scope & purpose of the study including the understanding of the plant & process steps that may influence the classification

— Previous data, if any

— References of applicable national and international hazardous area classification standards, codes and guidelines

— Considering Temperature Class and Gas Groups, Identification and compilation of flammability data

— Considering Statutory requirements

— Drawing a detailed Building and equipment layout of the facilities and physical verification and review of hazardous area classification zones

Consultivo, being one of the practicing Hazardous Area Classification Consultants in India provides review, assessment & consulting services globally.

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