Hazardous (Ex) Area Classification - Atex (2024)

Hazardous Area Classification for Flammable Gases and Vapours

Area classification may be carried out on typical Ex installations described in established codes, or by more quantitative methods that require a more detailed knowledge of the plant. The starting point is to identify sources of release of flammable gas or vapour. These may arise from constant activities; from time to time in normal operation; or as the result of some unplanned event. In addition, inside process equipment may be a hazardous area, if both gas/vapour and air are present, though there is no actual release. Some call it as ATEX Zoning / Ex Zoning / Area Classification / IECEx Area Classification

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”. In this context, ‘special precautions’ is best taken as relating to the construction, installation and use of apparatus, as given in BS EN 60079 -10¹.

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 apparatus to be used safely in that environment, taking into account the properties of the flammable materials that will be present. DSEAR specifically extends the original scope of this analysis, to take into account non-electrical 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: 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 most common values used are:

• Zone 0: Explosive atmosphere for more than 1000h/yr
• Zone 1: Explosive atmosphere for more than 10, but less than 1000 h/yr
• Zone 2: Explosive atmosphere for less than 10h/yr, but still sufficiently likely as to require controls over ignition sources.

A hazardous area extent and classification study involves due consideration and documentation of the following: Some call it as ATEX Zoning / Ex Zoning / Area Classification / IECEx Area Classification

• The flammable materials that may be present;
• The physical properties and characteristics of each of the flammable materials;
• The source of potential releases and how they can form explosive atmospheres;
• Prevailing operating temperatures and pressures;
• Presence, degree and availability of ventilation (forced and natural);
• Dispersion of released vapours to below flammable limits;
• The probability of each release scenario.

Ignition sources may be:

• Flames;
• Direct fired space and process heating;
• Use of cigarettes/matches etc;
• Cutting and welding flames;
• Hot surfaces;
• Heated process vessels such as dryers and furnaces;
• Hot process vessels;
• Space heating equipment;
• Mechanical machinery;
• Electrical equipment and lights
• Spontaneous heating;
• Friction heating or sparks;
• Impact sparks;
• Sparks from electrical equipment;
• Stray currents from electrical equipment
• Electrostatic discharge sparks:
• Lightning strikes.
• Electromagnetic radiation of different wavelengths
• Vehicles, unless specially designed or modified are likely to contain a range of potential ignition sources

A hazardous area can be defined as any location where there is risk of an explosion. But every hazardous area is different and each has specific requirements depending on the nature of the atmosphere and the elements that are present.

Fundamentally, for an explosion to take place, flammable or explosive gases, vapours, mists or dusts will be present. Then, the level of risk of an explosion is based on the frequency and duration of the occurrence of an explosive atmosphere. This level of risk is represented by classifying the hazardous area as Zone 0, Zone 1 or Zone 2 (for gas, vapour and mist atmospheres) or Zone 21 or Zone 22 for dust atmospheres.

In this article we will look at what defines Zone 0, Zone 1 and Zone 2 hazardous area classifications and the considerations for specifying lighting into each area. But first, we must consider what is likely to cause an explosion in the first place. Some call it as ATEX Zoning / Ex Zoning / Area Classification / IECEx Area Classification

There are three necessary components for an explosion to occur;

Where there is potential for an explosive atmosphere, special precautions are needed to prevent fires and explosions. Electronic equipment, including lighting, needs to be purpose designed for use in hazardous areas to prevent a spark occurring and igniting any flammable substances.

Although every application is different, for the ease of monitoring and specification each hazardous area is classified as a particular level or “zone”. As a result, all hazardous area equipment must be designed with hazardous area zone classifications in mind, as the “zone” governs the level of protection and precaution required. It is essential to know which zone you are working in, so that you can specify the most appropriate equipment.

For gases, vapours and mists the zone classifications are recognised as Zone 0, Zone 1 and Zone 2 areas. Let’s take a look at what defines each zone…

Zone 2 is a place in which an explosive atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only. These areas only become hazardous in case of an accident or some unusual operating condition.

To make this even easier to understand, take a look at the diagram of a typical petrol station below where we have identified the areas that are classified as Zone 0, Zone 1 and Zone 2.

Whenever you are filling up your tank you are standing in a Zone 1 hazardous area. That is why the use of mobile phones on petrol forecourts are banned. You’re phone isn’t rated for use in hazardous areas. Have a think about it next time you’re filling up!

A type of explosion protection where precautions are taken so that hazardous area electricalequipment that has the potential to arc is not capable of igniting asurrounding explosive atmosphere. This can be further categorisedas follows:

Ex nA -Where components used in construction are non-sparking
Ex nC -Where components used in construction are non-incendive
Ex nR – Where components used are tightly enclosed torestrict the breathing and prevent ignition
Ex nL -Where componentsused in construction do not contain enough energy to cause an ignition

ATEX certification requirements vary depending on the category of equipment and the zones of the equipment’s intended use.

We perform ATEX testing on materials, such as air powered drills or turbine assemblies that are going into an ATEX Zone and can potentially generate and store a static charge. These tests give you confidence in the materials used and the pace of mind. However, as they pose no actual ignition risk in themselves, the products cannot be ATEX certified. For example, with a plastic bucket, although there could be a small buildup of static, the bucket in itself cannot cause a spark or discharge and therefore would not be a risk.

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For more support and if you’d like to discuss your ATEX and IECEx requirements in more details,contact us today. Our Experts are ready to guide you through our capabilities and highlight if there may be any barriers to certifying your ATEX / IECEx product.