1. Overview of Explosion Protection
1-7
TI 33Q01J30-01E
Classification of Explosive Gas
Classification of Explosive gas (vapor) involves a division by explosion intensity and a division by
explosion energy. Classifications in the technical standard, IEC, ATEX, and UKEX are listed in
the following table.
Table Classification of Explosive Gas
Classification
Flame-proof enclosures
Intrinsic safety
Major gas
Maximum gap in mm
where the fire runs, when
the depth of joint surface is
set to 25 mm
Minimum ignition current ratio of the
target gas, when the minimum ignition
current of methane, which is calculated
by spark ignition test equipment, is
assigned 1
II A
0.9 or more
More than 0.8
Propane
II B
More than 0.5, 0.9 or less
0.45 or more, 0.8 or less
Ethylene
II C
0.5 or less
Less than 0.45
Hydrogen, Acetylene
The United States and Canada have another classification.
Dec. 3, 2021-00
