The ATEX guidelines apply to all places where there is a risk of explosion.
The guidelines have a broad scope and include both gas explosion hazards and dust explosion hazards.
The ATEX Directive 2014/34/EU provides regulations for products used in an explosive atmosphere.
The different environments are divided into three zones. A separate ATEX certification applies to all zones.
• Gas zone 0, 1 and 2
• Dust zone 20, 21 and 22
The use of explosion-proof equipment in an explosion-hazardous environment is only possible with equipment that is correctly marked. The type plate of the device always contains a clearly legible marking with regard to the safety level.
The type plate is constructed as follows.
For example: II 2G Ex de IIC T4
(A) II = Group classification as defined in 2014/34/EU
(B) 2G = Zone classification (2014/34/EU)
(C) Ex = explosion-proof
(D) de = material protection method (EN IEC 60079-0)
(E) IIC = gas group (or substance group in case of IIIC)
(F) T4 = Temperature class
Material groups and categories (A)
At the moment there are 2 material groups:
• Material group I concerns all underground (mining) installations;
• Material group II concerns all other above-ground installations.
Material group II is divided into 3 gas groups. The distinction lies mainly in the MESG (Maximum Experimental Safety Gap)
for pressure-resistant encapsulation and the MIE (Minimum Ignition Energy) for intrinsically safe circuits.
Zone classification (B)
In order to determine the extent to which measures are necessary to avoid active ignition sources, explosion-hazardous areas must be divided into zones according to the regularity and duration of the presence of explosion-hazardous gas or dust.
| Zone 0 of 20 | Gas or dust constantly present | More than 1000 hours per year |
| Zone 1 of 21 | Gas or dust likely present occasionally | Between 10 and 1000 hours per year |
| Zone 2 of 22 | Gas or dust if present for short duration | Less than 10 per year |
Ex marking (C)
Explosion prevention marking (EX). Indication that the product is explosion-proof.
Protection method (D)
There are many possible methods of protection against ignition. Here are the most commonly used methods of protection for gas explosion safety.
| Ex d – pressure-resistant enclosure | NEN – EN – IEC – 60079 – 1 |
| Ex e – heightened – increased security | NEN – EN – IEC – 60079 – 7 |
| Ex p – pressurization – internal overpressure | NEN – EN – IEC – 60079 – 13 |
| Ex i – intrinsic safety | NEN – EN – IEC – 60079 – 11 |
| Ex n – non-ignitable. Only for category 3G (zone 2) | NEN – EN – IEC – 60079 – 15 |
| nA = non-sparking, nC = closed construction, nR = limited breathing |
Gas and dust groups (E)
Representative gases or vapors of liquids are:
| Inling | Feature | Representative material |
| I | Mining gas = 210 uJ | Methane |
| IIA | Ignition energy > 200 uJ | Propane, butane, kerosene |
| IIB | Ignition energy 60 – 200 uJ | Ethylene, hydrogen sulfide, ethyl ether |
| IIC | On-screen energy 20 – 60 uJ | Hydrogen, acetylene, carbon disulphide |
Because more and more EN (European Norms) are based on IEC (International Norms), we are also dealing with the new dust groups III in Europe. These are subdivided into IIIA, IIIB and IIIC. The subdivision is characterised as follows:
| Layout | Feature | Representative material |
| IIIA | Fibers and flakes > 0.5 mm | Tobacco, coarse sawdust |
| IIIB | Electrically non-conductive <0.5 mm | Milk powder |
| IIIC | Electrically conductive <0.5 mm | Graphite powder |
NB: IIC falls within the range of IIB etc… IIC is the lowest in ranking. IIA is therefore the ‘heaviest’ version.
Temperature classes and maximum surface temperature (F)
When a flammable gas mixture or dust cloud comes into contact with an object with a temperature equal to or higher than the ignition temperature of this flammable gas or dust, ignition can occur. For example, heating elements, mechanical drives, electric motors and light bulbs.
Gas explosion-proof equipment is classified into temperature groups or “T-classes”. The equipment, which is classified into a certain temperature class, may therefore be used for gases with an ignition temperature that is higher than the temperature belonging to that group.
Classification principle (norm. EN 50 014)
| 11 | Ignition temperature 450°C |
| 12 | Ignition temperature 300°C |
| 13 | Ignition temperature 200°C |
| 14 | Ignition temperature 135°C |
| 15 | Ignition temperature 100°C |
| 16 | Ignition temperature 85°C |
NB: T1 falls within the range of T2 etc… T1 is the lowest in ranking. T6 is therefore the ‘heaviest’ version.
Guidelines
As of 20 April 2016, ATEX 95 has been replaced by ATEX 114 (Directive 2014/34/EU) and ATEX 137 (Directive 1999/92/EC) has a new name, namely ATEX 153. According to the European Commission, the names ATEX 114 and ATEX 153 are only ‘informal’ names. The correct legal names are Directive 2014/34/EU and Directive 1999/92/EC.
All new explosion-proof equipment and protective systems must comply with the new directive as of 20 April 2016.
This mainly affects manufacturers of explosion-proof equipment and protective systems.
For example, explosion-proof equipment that complies with the ATEX 114 regulations must be marked with the ‘Ex’ symbol in a regular hexagon. There is no obligation for a yellow background here. There will be more product supervision, stricter requirements for importers and new accreditation for ‘notified bodies’.
It is important for users to know that the current ATEX 95 certificates remain valid. However, as soon as explosion-proof equipment or protective systems are modified or renewed, ATEX 114 applies.
The difference between the two directives is that ATEX 114 is applied to the manufacturing of installations and products (devices CE directive) and ATEX 153 is applied to the environment, procedures, instructions of employees (social directive), both in Ex environments. The aim of this combination of directives is to guarantee the safety and health of employees in areas with explosion hazard. In addition, ATEX 114 contributes to the free trade within the EU, for equipment and safety systems that are used in these areas.
