33
Explosion
group
Temperature class
T1
(450 °C)
T2
(300 °C)
T3
(200 °C)
T4
(135 °C)
T5
(100 °C)
T6
(85 °C)
IIA
Acetone (540 °C)
Ethane (515 °C)
Propane (470 °C)
Toluene (535 °C)
Cyclohexanone (430 °C)
i-amyl acetate (380 °C)
n-butane (365 °C)
n-butyl alcohol (340 °C)
Petrol (220 °C–300 °C)
Diesel (220 °C–300 °C)
Heating oil (220 °C–300 °C)
n-hexane (240 °C)
Acetaldehyde (140 °C)
–
–
IIB
Town gas (560 °C)
Ethyl alcohol (425 °C)
Ethylene (425 °C)
Ethylene oxide (440 °C)
Hydrogen Sulfide (270
°C)
Ethyl ether (180 °C)
–
–
IIC
Hydrogen (560 °C)
Acetylene (305 °C)
–
–
–
Carbon disulfide (95 °C)
Ex zone gases,
vapors, mists
(EN 60 079-10)
Unit
category
A dangerous,
potentially explosive
atmosphere ...
No effective ignition
source ...
Zone 0
1G
... is present either conti
nously or for lengthy
periods (>1000 hours/
year)
... in fault-free operation,
for rare operational faults
or in the event of fre-
quent operational faults
Zone 1
2G
... only occurs occasionally
(10 - 1000 hours/year)
... in fault-free operation
or with frequent opera-
tional faults
Zone 2
3G
... occurs infrequently, and
then only for a short
time (<10 hours/year)
... in fault-free operation
Making the right choice –
Selection criteria for electrical equipment
Division of flammable gases and vapors into
explosion groups and temperature classes
Explosion group I
Explosion group II
Electrical equipment for use in mining operations with a firedamp risk,
e.g. coal-mining: coal dust, methane gas
Electrical equipment for use in all areas with an explosion hazard, other than mining
operations with a firedamp risk, e.g. the chemical industry: paints, acetylene
Explosion groups
Temperature
class
Maximum permissible
surface temperature of
the equipment
Ignition temperature
of the flammable
material
T 1
450 °C
> 450 °C
T 2
300 °C
> 300 °C
≤
450 °C
T 3
200 °C
> 200 °C
≤
300 °C
T 4
135 °C
> 135 °C
≤
200 °C
T 5
100 °C
> 100 °C
≤
135 °C
T 6
85 °C
> 85 °C
≤
100 °C
-proof Execution
Temperature classes in
explosion group II
