Apparatus group 

In de IEC / CENELEC marking of the protection method there is also an apparatus group (I for mines, II other). In the NEC 500 this is called the apparatus class (Class I for gasses, Class II for dust and Class III for fibers).

Gas group 

The apparatus group is supplemented by the IEC / CENELEC with the gas group  (A, B or C) and by the NEC 500 met de gas group (A - D for gasses and E - F for dust).

The gas group related for Ex d to the Minimum Experimental Safe Gap (MESG) and for Ex i to the Minimum Ignition Current (MIC).

Temperature classification

The temperature class is related to the Auto Ignition Temperature (AIT) of the gas.

 

Indication of the classification of several gasses
IEC / CENELEC NEC500 T1
450 C
T2
300 C
T3
200 C
T4
135 C
T5
100 C
T6
85 C
I Mining* Methane          
IIA Class I/Group D Acetone
Ethane
Ethyl ethanoate
Ammonia
Benzol (pure)
Ethanoic acid
Carbon oxide
Methane
Methanol
Propane
Toluene
Ethanol
i-Amyl acetate
n-Butane
n-Butyl alcohol
Benzine
Diesel fuel
Aircraft fuel
Heating oils
n-Hexane
Acetaldehyde
Ethylether
   
IIB Class I/Group C Coal gas
(lighting gas)
Ethanol
Ethylene
       
(Group IIB + H2)
IIC
Class I/Group B
Class I/Group A
Hydrogen  Acetylene        Carbon disulphide

* Not within scope of NEC. Under jurisdiction of MSHA
The above data are indicative. Certain gasses have been moved to new gas groups with the publication of IEC 60079-20-1:2010. Exalon Delft assumes no responsibility for the accuracy of the data on this web page.

 

The end-users area classification into Zones or  Divisions determines the demands on the equipment that may be used in those Zones or Division. When the types of gasses that may occur vary (bas in chemical tankers) the end user will demand IIC T6 , but may also be satisfied with  IIC T4. In the petrochemical and en bulk storage industry is IIB T4 often satisfactory.