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Tablet - ATEX (Ex) Classification of Apparatus in hazardous area.

ATEX 100a

This term indicates compliance with the 94/9/EU directive, wich prescribes European-wide guidlines for handling equipment and protective systems in potensially explosive atmospheres. As of 1.July 2003, these regulations will be binding and thereby gurantee free movement of EX products in the EU. From this date on, products that were developed and manufactured in accordance with national EX standards may no longer be traded. This ends the transitional period for operators of facilities. From this date on only facilities that have been approved under ATEX may be operated. One provision, in particular, that is new is that now areas that are subject to dust exposuere are included in the ATEX. Operations where dust accumulates or is processed must therefore come to terms with the new directives.

In accordance with the various properties of gases with regard to ignition temperature, ignition capability and flame transmission capacity, explosion-protected electrical apparatus is divided into explosion groups and temperatur classes.

Division of explosion-protected apparatus into explosion groups.

  • Group I:
    • Electrical aparatus for use in mines susceptible to the hazard of firedamp.
  • Group II:
    • Electrical apparatus for use in all other hazardous areas.

A further sub-division of the Explosion Group II into "A", "B" and "C" is prescribed for the types of protection "flameproof enclosure" and "intrisic safety", as well as for "increased safety" with regard to relectrostatic requirements.

This is also for the protection types nC and nL. With the type of protection"flameproof enclosure" this sub-division is made according to the maximum experimental safe gap for the nontransmission of an internal ignition (MESG), whereas with the type of protection "intrinsic safety" this sub-division is made according to the ratio of the minimum ignition current of the mixture being teste to the minimum ignition current of a mixture of laboratory methane and air (MIC). Group II C aparatus is suitable for use in all types of gas atmospheres.

Division of explosion-protected apparatus into Explosion Groups and temperature classes.

  T1 T2 T3 T4 T5 T6
I Methan          
IIA Acetone, Ethan
Acetic acid
Methanol, Propane
IIB Town gas
(lamp gas)
IIC Hydrogen Acetylene        

Division of explosion-protected aparatus into temperature classes.

The ignition temperature is the lowest temperature of a surface at wich an explosive atmosphere will ignite. Gases and vapours can be divided into temperature classes according to their ignition temperatures. This results in a subdivision of explosion-protected electrical apparatus into the temperature classes T1 to T6. This classification allows explosion-protected apparatus to be used economically. The maxium surface temperature of an apparatus must always be lower than the ignition temperature of the gas/air or vapour/air mixture.

Generally speaking, explosion-protected apparatus must be suitable for an ambient temperatur from -20 °C to +40 °C. The following table show the temperature classes.

Division of explosion-protected apparatus into temperature classes.

Maximum Surface Temperature IEC / NEC® NEC 500 / Table 500.8(C)
450°C (842°F) T1 T1
300°C (572°F) T2 T2
280°C (536°F)
260°C (500°F)   T2B
230°C (446°F)   T2C
215°C (419°F)   T2D
200°C (392°F) T3 T3
180°C (356°F)
165°C (329°F)   T3B
160°C (320°F)   T3C
135°C (275°F) T4 T4
120°C (248°F)   T4A
100°C (212°F) T5 T5
85°C (185°F) T6 T6


It is the user's responsibility to ascertain if a particular product is safe and without risk to health and safety by virtue of its location in a hazardous area, i.e. classification of zones, gas groups, ignition temperatures, etc. Both the specifier and user should be thoroughly familiar with standard mentioned on this sites or any document within.

Whilst every care has been taken in the compilation of this document, we regrets that it connot accept responsibility for any errors or omissions contained herein. Readers should not rely upon the information contained in this document or site without seeking specific safety advice and ensuring that their own particular circumstances are in accordance with the matters set out.

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