Ex-pert Electrical Technologies

Dynamic elaboration on the Art & Science of Hazardous Area Protection

9.Reading an Ex Label


One thing is sure that the Ex Labels or Markings are never written in GREEK and there is no ‘fine print ‘ or any ‘between the lines‘  information.

In fact the Ex Labels/ Tags or the Markings on the Electrical components , manufactured for use in the Hazardous areas are “Regional Language Free”.

A system of symbols & alpha-numeric characters is used to fully describe the characteristics and operational parameters of the relevant electrical component.

Let us see the following label of a Junction Box

expeltec small JB

The LABEL or the MARKING should be clearly visible on a main part or the exterior of the equipment, prior to the installation and should remain visible after the installation.

Let us check the marking for the following points:

  1. It should have the name of the manufacturer.
  2. Manufacturer’s type code (Product Catalogue Number )
  3. Serial Number (If there is enough space)
  4. The NAME or the MARK of the Certifying body and the Certificate Reference in the following form:
        [NAME of the Certifying Body[YEAR-last 2 digits] [CERTIFICATE NUMBER]  
     5.  SYMBOL ‘X’. If some specific conditions of use are required. (The manufacturer may put other advisory markings as an  alternate)    
       6.  THE Ex MARKING  (See details below):

The Ex Marking


  • a)                  It starts with the Ex Symbol
  • b)                  The symbol of the TYPE of PROTECTION incorporated in the  equipment as below:-
expeltec IEC Marking 1
(Ref: IEC 60079-0)

( G stands for the Gas & M stands for the below-surface or MINES with firedamp)

  • c)                             The symbol of the group  (Equipment Group I or Group II )             

– I for electrical equipment for mines susceptible to firedamp;
– IIA        or        IIB          or          IIC            for electrical equipment for places with an explosive gas atmosphere other than mines susceptible to firedamp.
When the electrical equipment is for use only in a particular gas, the chemical formula or the name of the gas in given in parentheses.
When the electrical equipment is for use in a particular gas in addition to being suitable for use in a specific group of electrical equipment, the chemical formula shall follow the group and be separated with the symbol “+”, for example, “IIB + H2”.

[GAS Group IIB + H2:- It simply means that the equipment is safe for use in GAS Group IIB and additionally, it is also and only safe in Hydrogen filled areas. Hydrogen itself belongs to GAS GROUP IIC. (IEC 60079-0- edition 6)

(NOTE 1 Equipment marked “IIB” is suitable for applications requiring Group IIA equipment.
Similarly, equipment marked “IIC” is suitable for applications requiring Group IIA and Group IIB equipment.)

Table 3 – Relationship between gas/vapors or dust subdivision and equipment groups

gas group in relation to equipment groupNOTE : Equipment group II can be used with all GAS GROUPS

expeltec gas group 1

  • d.          Temperature Class  (Complete Temperature Class information is to be included in the Certificate )

  • e.           The equipment protection level  (as below) :-

Ga     or             Gb           or            Gc              or             Ma            or            Mb

  • f.             Ambient Temperature for the operation . (Electrical equipment designed for use in normal temperature range of -20°C to +40ºC does not require marking of the Ambient Temperature range . Equipments designed for use in other than this range is considered special . In this case the marking or the label will have the symbol Ta or T amb. together with both the upper & lower ambient temperatures or if this is not possible due to small space of the label then symbol X wiil be used to indicate special conditions of use.)


expeltec label details

Marking ( As per updated IEC documents )

New Label

(Another Example)

Tag Plate

Labels for Explosive Dust Atmosphere

Same first 5  rules,as that for the Explosive Gas Atmosphere, apply for the Explosive Dust Atmosphere  (EDA).  The difference is the Protection Type , as in the following detail:-

  • Start with the Ex Symbol followed by the type of protection or its level.

expeltec dust protection

(Ref: IEC 60079-0)

  • The symbol of the Explosive Dust GROUP

IIIA                                                            IIIB                                                            IIIC

  • The Maximum Surface Temperature  in degrees Celsius .  Example : T 75 ºC

For Group III Equipments. The complete information about the Multiple Maximum Temperatures ( with dust layer etc.)

should be included in the certificate.

Last But not least

Do study the relevant Ex Certificate.

(For Associated Apparatus see the post  Associated Apparatus)


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