Gas groups and temperature classes

Two characteristics of the gas determine the equipment to install: how easily an explosion propagates (the group) and the temperature at which it ignites spontaneously (the temperature class).

Gas groups

Group	Representative gas	Severity	Examples
IIA	Propane	Least severe	Propane, butane, industrial methane, petrol, acetone
IIB	Ethylene	Intermediate	Ethylene, ether, hydrogen sulphide
IIB+H2	Ethylene and hydrogen	IIB and hydrogen	Hydrogen installations without acetylene or carbon disulphide
IIC	Hydrogen, acetylene	Most severe	Hydrogen, acetylene, carbon disulphide

IIC equipment is suitable for all gases, subject to its temperature class. IIB+H2 equipment is also suitable for IIA gases. IIB equipment is suitable for IIB and IIA gases. Our IIB+H2 enclosures

Dust groups

Group	Type of dust
IIIA	Combustible flyings (fibres)
IIIB	Non-conductive dusts (flour, sugar, plastics)
IIIC	Conductive dusts (metals, carbon)

Temperature classes

The maximum surface temperature of the equipment must stay below the auto-ignition temperature of the gas.

Class	Maximum surface temperature
T1	450 °C
T2	300 °C
T3	200 °C
T4	135 °C
T5	100 °C
T6	85 °C

T6 equipment is suitable for all classes. For dusts, the surface temperature is given directly in degrees (for example T85 °C).