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Hazardous Areas - Protection Techniques according European IECEx

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Electronic or electrical equipment of any type for use in European hazardous areas must be ATEX certified as required by the EU directive 94/9/EC - also known as the ATEX directive.

Basis for equipment certification is the hazardous area classification system used, the

Ex marking

The ATEX directive classifies equipment into groups and categories which are defined by the marking on the equipment. A typical marking can be 

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Ex Classification - Equipment Marking
0158 II 2G EExd IIB T4
Type of
Type of
Sub Group

The different parts of the nomenclature are explained below:

CE Mark

Informs that the product complies with the European Directive.

Notified Body Code

Informs witch official Notified Body did the testing and certification of the product.

Explosion Proof

The explosion proof Ex tag is required for certified equipment in accordance with the ATEX directive.

Equipment Group

The tag for equipment group relates to groups in the Zone system where

  • I - is for use in underground mines
  • II - is for all other places

Category - Gas/Dust


The tag for category relates to the Zone in the Zone system where

  • 1 - is for equipment for use in areas where an explosive atmosphere is present continuously or for long periods or frequently
  • 2 - is for equipment for use in areas where an explosive atmosphere is likely to occur in normal operations
  • 3 - is for equipment for use in areas where an explosive atmosphere is unlikely to occur in normal operations


  • G - equipment certified for flammable gases
  • D - equipment certified for dust atmosphere

Type of Certificate - Type of Protection

Type of Certificate

Types of certificate indicates standards used for the certification.

  • EEx - European standards
  • AEx - American standards

Type of Protection

Types of protection indicates the level of protection concepts the equipment is designed for. The protection concepts are divided in to sub classes.


Protection applied by encasing the components in a resin type material.

The protection is referred to as "Ex m".

Sub divisions ma for Zone 0 and mb for Zone 1.


The enclosure can withstand the pressure developed during an internal explosion of an explosive mixture. The explosion is not transmitted to the explosive surrounding atmosphere and the enclosure operates with a temperature to low for the surrounding explosive gas or vapor to ignite.

This protection is referred to as "Ex d".

Intrinsically Safe

Electrical equipment is under normal or abnormal conditions incapable of releasing sufficient electrical or thermal energy to cause a ignition of the hazardous surrounding atmospheric mixture.

This protection is referred to as "Ex i".

Sub divisions ia  for Zone 0, ib for Zone 1 and ic for Zone 2.

Increased Safety

High quality and very robust components. Various measures are applied to reduce the probability of excessive temperatures and the occurrence of arcs or sparks in the interior and on the external parts of the equipment. Increased safety may be used with flame-proof type of protection.

The protection is referred to as "Ex e".

Oil Filled

Protection applied by submerging the components in oil.

The protection is referred to as "Ex o".


Protection applied by keeping a positive pressure in the enclosure relative to the surrounding atmosphere with air or an inert gas. With an overpressure monitored, maintained and controlled - the surrounding ignitable atmosphere can not come in contact with energized parts of the apparatus.

The protection is referred to as "Ex p".

Sub divisions px or py for Zone 1 and pz for Zone 2.

Sand/Powder/Quartz Filled

Protection applied by covering the components with sand, powder or quartz.

The protection is referred to as "Ex q".

Non Incendive

A protection applied to electrical equipment in such a way that normal operation is not capable of igniting surrounding explosive atmospheres.

The protection is referred to as "Ex n".

Special Protection

Any method which can be shown to have the required degree of safety.

The protection is referred to as "Ex s".

Group - Sub Group

The tag for equipment group relates to groups in the Zone system where

  • IIA - Atmosphere containing propane, acetone, benzene, butane, methane, petrol, hexane, paint solvents or gases and vapors of equivalent hazard.
  • IIB - Atmosphere containing ethylene, propylene oxide, ethylene oxide, butadiene, cyclopropane, ethyl ether, or gases and vapors of equivalent hazard.
  • IIC - Atmosphere containing acetylene, hydrogen, carbon disulphide or gases and vapors of equivalent hazard.
  • IIIA - Atmosphere containing combustible flyings.
  • IIIB - Atmosphere containing non-conductive dust.
  • IIIC - Atmosphere containing conductive dust.

Temperature Classification

Hazardous area equipment is classified according to maximum surface temperature produced under fault conditions at ambient temperature 40 oC (104 oF), or as otherwise specified.

Ex Classification - Temperature Codes
Temperature CodeoFoCTypical Substances
T1 842 450 Hydrogen, Toluene, Ethyl acetate
T2 572 300
T3 392 200 Petrol, Gasoline, Diesel
T4 275 135
T5 212 100
T6 185 85
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Hazardous Areas - European Classification Standard

European hazardous area classification with zones, protection types, temperature codes and codes.

Hazardous Areas - North America Classification

North American hazardous locations classification with classes, divisions and groups

Hazardous Areas Protection Techniques for North America

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IP - Ingress Protection Ratings

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American National Standards Institutes schedule for safety colors marking physical hazards.

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