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  4. What does the information on a certification label or control drawing mean?
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  3. What does the information on a certification label or control drawing mean?

What does the information on a certification label or control drawing mean?

There is a lot of technical information on a certification label that helps to identify the area and conditions in which an electronic product can be used.

Training Course

All of the information below is covered in a training course called “Understanding Hazardous Locations Basics” which is available on our training page.

Label Information

Example Certification Label


This identifies the lab that was used to test and certify the product as safe. Follow the links below to navigate to the lookup for certification files based on the certifier.


Each class identifies a different type of flammable material.

Class I

This class refers to flammable gases or vapors and is typically seen in Oil and Gas

Class II

This class refers to combustible or electrically conductive dust. It is typically seen in farming (i.e. Grain Dust)

Class III

This refers to ignitable fibers or flyings in the air and is typically seen in manufacturing.

Zone and Division

Products can either be installed in a general purpose area or a hazardous area. These areas are broken up into different categories that are called Zones or Divisions depending on the standard used.

Comparison of Zones and Divs


Zone is used in the newer unified, international standard IEC 60079.

Zone 0

Explosive atmosphere continuous

Zone 1

Explosive atmosphere likely

Zone 2

Explosive atmosphere not normal


Division or Div has been used historically across a wide variety of standards in many different regions.

Div 1

Hazard exists in normal conditions

Div 2

Hazard exists in abnormal conditions

Ex Codes

The IEC 60079 standard is broken into a number of subsections. The Ex Code is used to distinguish type of protection.

Ex ia

Intrinsically safe for zones 0, 1, 2

Ex ib

Intrinsically safe for zones 1, 2

Ex ic

Intrinsically safe for zone 2

Ex d

Flameproof (explosion proof) zones 1, 2

Ambient Temperature

The temperature code specifies the maximum surface temperature of the product which helps set the ambient temperature rating of a product. The lower the surface temp, the higher the allowable ambient temp.

The major steps are identified with a number, but there are several steps in between identified with letter A – D.

Temperature CodeSurface Temperature
T2300 C/572 F
T3200 C/392 F
T4135 C/275 F
Common Temperature Codes

Gas Group

The gas group identifies the types of gases a product is approved for.

Zone Gas GroupDiv Gas GroupGases
IIADPropane, Methane
IIBCEthylene, Hydrogen Sulfide
IICA + BHydrogen, Acetylene

IIC is the most severe, while IIA is the least severe. A product can be installed in an area with the designated gas group or a less severe group.

Other Instructions

This often provides additional warnings and points the reader to the appropriate control drawing which contains more detail about the safe us of the product.

Control Drawing

A control drawing must be provided by the manufacturer that:

  • Identifies Acceptable Installation Zones
  • Details all connections with equipment outside the Zone
  • Lists entity parameters
    • Ratings for each connection
    • Includes Voltage, Current, Power, Capacitance, and Inductance
  • Warnings and special notes
Updated on 29 June 2020

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