ProMinent Sigma 3 Basic Operating Instructions Manual page 8

Identity code
You should always consider the explosion group AND
temperature class together:
You are safe in areas at risk from explosion with all the
gases listed in the table with equipment approved for
explosion group IIC and temperature class T4.
Equipment approved for explosion group IIB can also be
used for explosion group IIA – not for explosion group
IIC.
Equipment approved for temperature class T3 can also
be used for temperature classes T2 to T1 – not for tem‐
perature class T4.
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