CENELEC AND IEC NORMATIVES
THE ROLE OF THE IEC

This is the system developed by the International Electrotechnical Commission (IEC), which was established in 1904 and whose headquarters is in Geneva in Switzerland.
In 1947, with the creation of the International Standards Organization (ISO) by the United Nations, the IEC became responsible for the organization of the electrical division, while still remaining independent.

The IEC has defined three zones of gas and vapor classification:
• Zone 0 : the explosive atmosphere is continuously present.
• Zone 1 : the explosive atmosphere is often present.
• Zone 2 : the explosive atmosphere may accidentally be present.

Gas and vapor classification
(Tabelle – 1)
Gases are divided into four groups by the CEC and the NEC (with some additional gases).
The IEC also defines different groups of gases and vapors.
The IEC and North American groups are viewed as fundamentally the same, apart from the fact that there are three groups in the IEC and four for North America.
Temperature classification
(Tabelle – 1 bis)
The IEC has defined a temperature classification for equipment used in hazardous areas.
Following this, CEC and NEC have also been modified to include a temperature classification.
This temperature table is as follows
Group
Gas or Vapor
IEC
N. America
I I C
A
Acetylene
I I C
B
Hydrogen
I I B
C
Ethylene
I I B
C
Ethyl ether
I I B
C
Cyclopropane
I I B
C
Butadiene 1-3
I I A
D
Propane
I I A
D
Ethane
I I A
D
Butane
I I A
D
Benzenze
I I A
D
Pentane
I I A
D
Heptane
I I A
D
Acetone
I I A
D
Methyl Ethyl
I I A
D
Methyl Alcohol
I I A
D
Ethyl Alcohol
Temp. in
Degrees °C
Classification
IEC
N. America
450
T1
T1
300
T2
T2
280
T2
T2A
260
T2
T2B
230
T2
T2C
215
T2
T2D
200
T3
T3
180
T3
T3A
165
T3
T3B
160
T3
T3C
135
T4
T4
120
T4
T4A
100
T5
T5
85
T5
T6