HEYLO PowerVent 4200 EX Bedienungsanleitung Seite 21

Explosion groups, temperature classes
If the device group and device category determine in which zones an operating
material can be used, the explosion group and temperature class determine for which
media within the zone the operating agent can be used. The ignition protection type, on
the other hand, does not represent a quality characteristic, but is a constructive solution
selected for the operating material to implement explosion protection.
Gases-Mists-Vapours
Dust Particles
Safe Area Safe Area
Division into explosion groups
According to ignition protection type, explosion protected operating materials for gases,
mists and vapours are divided into three explosion groups(IIA-IIB-IIC). The explosion
group is a measure for the ability for ignition flashover of gases (atmosphere that can
explode). The requirements to the operating material increase from II A to II C.
IIA IIB IIC
Increasing requirement
Division into temperature classes
In the case of explosion protected operating materials installed within the ex area,
division takes place into six temperature classes (T1 to T6). The temperature class is
not – as is frequently wrongly interpreted – the temperature used for the operating
agent but the maximum permissible surface temperature that can be used on the
operating material, which, with reference to + 40° C ambient temperature, cannot be
exceeded at any point of the surface and at any time. The maximum surface
temperature must always be lower than the ignition temperature of the surrounding
medium. The requirements to the operating material increase from T1 to T6.
21 EN