
228 • Use in Hazardous Environments
Classification Meeting CENELEC and IEC
WAGO-I/O-SYSTEM 750
Bus System
6.3.2 Explosion Protection Group
In addition, the electrical components for explosive areas are subdivided into
two groups:
Group I: Group I includes electrical components for use in fire-damp
endangered mine structures.
Group II: Group II includes electrical components for use in all other
explosive environments. This group is further subdivided by
pertinent combustible gases in the environment.
Subdivision IIA, IIB and IIC takes into account that
different materials/substances/gases have various ignition
energy characteristic values. For this reason the three sub-
groups are assigned representative types of gases:
IIA – Propane
IIB – Ethylene
IIC – Hydrogen
Tab. 6-1: Minimal ignition energy of representative types of gases
Minimal Ignition Energy of Representative Types of Gases
Explosion group I IIA IIB IIC
Gases Methane Propane Ethylene Hydrogen
Ignition energy (µJ) 280 250 82 16
Hydrogen being commonly encountered in chemical plants, frequently the
explosion group IIC is requested for maximum safety.
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