Classes of Explosive Atmospheres � EU Classification

An understanding of this classification is required because often motors and other electrical equipment are required to be installed in these hazardous or explosive atmospheres. A clear understanding of the classes of explosive atmospheres will help in the selection and specification of electrical equipment in such environment.

Classes of Explosive Atmospheres
The EU (European Union) ATEX directive 99/92/EC distinguishes between two types of explosive atmospheres: GAS and DUST. Areas subjected to these two kinds of explosive atmospheres are each divided into three zones. Each zone characteristics are identical for gas and dust, but their numbering is different. Zones 0, 1, 2 refer to gas and zones 20, 21, 22 refer to dust. 

The various classes of explosive atmospheres are listed below
with a description of the characteristics of each one of them including the level of danger present and what category of equipment are required to be installed in such explosive atmospheres.

Zones	Description	Level of Danger to User	Type of Equipment Required
0/20	Permanent presence of explosive gasses or combustible dust. Minimum category 1 equipment required for use	Constant Danger	Category 1
1/21	Occasional presence of explosive gasses or combustible dust during normal duty. Minimum category 2 equipment required for use	Potential Danger	Category 2
2/22	Presence of explosive gasses or combustible dust not likely to occur or only for a shorter period of time. Minimum category 3 equipment required for use	Minor Danger	Category 3

A category 1 equipment is an equipment that can safely work in a zone  0 or 20 explosive atmosphere.
A category 2 equipment is an equipment that can safely work in a zone  1 or 21 explosive atmosphere.
A category 3 equipment is an equipment that can safely work in a zone  2 or 22 explosive atmosphere.

The EU classification of hazardous or explosives atmosphere is somewhat different from the North America classification but the zones (EU) and class (North America) categorization have similar characteristics. See Hazardous Area Classification