ATEX: Classifications & Definitions

In areas where there’s a risk of explosion, supplying and using equipment deemed as safe for use in these environments (ATEX equipment) is both essential for the safety of people in the environment and essential for preventing an ignition in the atmosphere.

There are many different causes that can directly create an explosive atmosphere. Learning to define, spot and take action against these is of the utmost importance for everyone working within these environments and it is the responsibility of an employer to make sure that staff are supplied with the training and equipment they need to work safely within these areas.

The following text explores the different classifications given to areas and equipment and explains how they come together to form an ATEX rating.

Area Classifications

In Europe, areas are defined as a Zone depending on the type of hazard. In America, the same applies but are classified as Divisions.

The following table outlines the type of zones/divisions possible and how they are classified.

European & IEC ClassificationDefinition of Zone or DivisionNorth American Classification
Zone 0 (Gases) - "G"An area in which an explosive mixture is continuously present or present for long periodsClass I Division 1 (Gases)
Zone 20 (Dusts) - "D"An area in which an explosive mixture is continuously present or present for long periodsClass II Division 1 (Dusts)
Zone 1 (Gases) - "G"An area in which an explosive mixture is likely to occur in normal operationClass I Division 1 (Gases)
Zone 21 (Dusts) - "D"An area in which an explosive mixture is likely to occur in normal operationClass II Division 1 (Dusts)
Zone 2 (Gases) - "G"An area in which an explosive mixture is not likely to occur in normal operation and if it occurs will exist only for a short timeClass I Division 2 (Gases)
Zone 22 (Dusts) - "D"An area in which an explosive mixture is not likely to occur in normal operation and if it occurs will exist only for a short timeClass II Division 2 (Dusts)
Class III Division 1 (Fibres)
Class III Division 2 (Fibres)

Gas Groups

Gas can be extremely volatile; learning to classify the gas in an area and using equipment certified as safe for use with that gas is essential to prevent ignition.

Generally gasses are classed into two groups, Group I – Mining and Group II – Surface Industries.

Typical Gas/MaterialEuropean/I.E.C Gas GroupNorth American Gas Group
MethaneI-
AcetlyeneIICA
HydrogenIICB
EthyleneIIBC
PropaneIIAD
Metal Dust-E
Coal Dust-F
Grain Dust-G

The ‘I’ symbol referenced above refers to the device group as being suitable for mining. The ‘II’ symbol denotes use in other explosive areas.The A, B and C symbols are used to show the volatile nature of a gas in the environment. A is the least volatile, B is medium-danger and C is highly dangerous gasses such as Hydrogen. So if a piece of equipment has a IIC rating, this means it is suitable for use in highly dangerous gas environments.

Classifying Temperature

Sometimes all it takes to ignite the atmosphere can be a rise in temperature. This can be anything from a hot surface to a piece of equipment gradually rising in heat during use.

All electrical equipment to be used in hazardous environments is classified according to the maximum surface temperature it will reach during use. Each piece of equipment is designed with a ‘T’ rating along with a number (which varies depending on American/European classifications).

The following table outlines the different classifications for temperature.

Temperature ClassificationMaximum Surface Temperature
European/I.E.CNorth American
T1T1450°C
T2T2300°C
T2A280°C
T2B260°C
T2C230°C
T2D215°C
T3T3200°C
T3A180°C
T3B165°C
T3C160°C
T4T4135°C
T4A120°C
T5T5100°C
T6T685°C

 

Next Page: Understanding ATEX Codes >>

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